Model Comparison: Conventions of Standard English

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Gemini 3 Pro

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What You Need to Know

• This is the heavyweight category. Conventions of Standard English (CSE) accounts for approximately 51–56% of the ACT English test (roughly 38–42 questions). Mastering these rules is the fastest way to improve your score.
• It relies on rules, not your ear. While reading aloud in your head helps, the ACT intentionally designs questions that "sound" okay but are grammatically incorrect. You must learn to spot the mechanical structure of sentences.
• Punctuation is logical. Commas, semicolons, and colons are not

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GPT 5.2 Pro

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What You Need to Know

• ACT English is passage-based editing: you choose the clearest, most grammatically correct option for an underlined portion (often including NO CHANGE, DELETE, and punctuation-only choices).
• Conventions of Standard English (per ACT’s official reporting categories) is the grammar-and-usage portion—typically the largest share of English questions—so clean rules and fast pattern recognition matter.
• When multiple answers are “grammatical,” pick the one that is most standard, clear, and concise while matching the sentence’s meaning and logical relationships.

Sentence Structure and Formation

Sentence structure is how clauses and phrases are built into a complete thought.

Core rule: independent vs. dependent clauses

• Independent clause: can stand alone as a sentence.
• Dependent clause: starts with a subordinating word (e.g., because, although) and cannot stand alone.

Build correct sentences

• Simple: 1 independent clause.
• Compound: 2+ independent clauses joined correctly.
• Complex: independent + dependent clause.

Example

• Correct: “The exhibit opened early, and the crowd arrived at noon.”
• Correct: “Although the exhibit opened early, the crowd arrived at noon.”

Exam Focus

• Why it matters: Many ACT questions test whether you can spot what a sentence is (clause types) before fixing punctuation.
• Typical question patterns:
  • Pick the option that correctly joins clauses.
  • Choose punctuation that matches the sentence’s clause structure.
• Common mistakes:
  • Treating a dependent clause as a complete sentence.
  • Adding a comma where a stronger join (semicolon/period) is needed.

Run-On Sentences and Comma Splices

A run-on is two independent clauses joined with no valid connector. A comma splice uses only a comma to join independent clauses.

Fixes for two independent clauses

• Period: “I practiced. I improved.”
• Semicolon: “I practiced; I improved.”
• Comma + FANBOYS conjunction (for, and, nor, but, or, yet, so): “I practiced, so I improved.”
• Subordination: “Because I practiced, I improved.”

Example (comma splice → fix)

• Wrong: “The bus was late, I walked.”
• Right: “The bus was late, so I walked.” / “The bus was late; I walked.”

Exam Focus

• Why it matters: This is a high-frequency ACT grammar trap—especially when answers differ only by punctuation.
• Typical question patterns:
  • Choose between comma/semicolon/period when both parts could stand alone.
  • Replace a splice with a subordinating clause.
• Common mistakes:
  • Using a comma alone to join two complete sentences.
  • Adding “and” without checking meaning (and vs. but vs. so).

Sentence Fragments

A fragment lacks an independent clause (often missing a subject, a finite verb, or a complete thought).

Common fragment types

• Dependent-clause fragment: “Because the forecast changed.”
• Phrase fragment: “Running through the hallway.”
• Relative clause fragment: “Which surprised everyone.”

Fixes

• Attach to a nearby independent clause.
• Add a subject/verb or revise into a full sentence.

Example

• Fragment: “Which the committee approved.”
• Fix: “The plan, which the committee approved, moved forward.”

Exam Focus

• Why it matters: ACT often hides fragments with tempting punctuation choices (especially periods).
• Typical question patterns:
  • Decide whether to use a period or a comma.
  • Combine a fragment with the sentence before/after.
• Common mistakes:
  • Inserting a period before “because/which/although.”
  • Leaving an -ing phrase as a “sentence.”

Parallel Structure

Parallel structure means items in a list or comparison follow the same grammatical form.

Where parallelism appears

• Lists: nouns with nouns, verbs with verbs, clauses with clauses.
• Paired structures: both/and, either/or, neither/nor, not only/but also.
• Comparisons: “more X than Y” (same form on both sides).

Example

• Wrong: “She likes hiking, to swim, and bikes.”
• Right: “She likes hiking, swimming, and biking.”

Exam Focus

• Why it matters: Parallelism is a “style-as-grammar” skill the ACT tests with small wording changes.
• Typical question patterns:
  • Fix a list so all items match.
  • Repair paired constructions (either/or, not only/but also).
• Common mistakes:
  • Mixing verb forms (to run vs. running).
  • Fixing one item but forgetting the rest of the list.

Coordination and Subordination

Coordination joins equals (independent clauses or similar items). Subordination shows one idea depends on another.

Coordination tools

• FANBOYS with a comma (for independent clauses).
• Semicolon (independent clauses).

Subordination tools

• Subordinating conjunctions: because, although, when, while, since.
• Relative pronouns: who, which, that.

Meaning matters

• Coordination suggests equal weight.
• Subordination highlights cause, contrast, time, condition.

Example

• Coordination: “I studied, and I passed.”
• Subordination: “Because I studied, I passed.” (cause emphasized)

Exam Focus

• Why it matters: Many questions test whether your connector matches logic (cause vs. contrast) and structure.
• Typical question patterns:
  • Choose between “and/but/so” or “because/although.”
  • Decide whether to make one clause dependent.
• Common mistakes:
  • Using “since” when time vs. cause is unclear.
  • Picking a grammatically fine connector that changes meaning.

Commas, Semicolons, and Colons

Punctuation choices often signal clause boundaries and relationships.

Commas

Use a comma for:

• Introductory elements: “After the show, we left.”
• Nonessential (parenthetical) information: “My brother, who lives abroad, is visiting.”
• Items in a series.
• Before FANBOYS joining independent clauses.

Semicolons

Use a semicolon to join two related independent clauses (or in complex lists).

Colons

A colon introduces what follows—often a list, explanation, or example—and it typically comes after an independent clause.

Example

• Colon: “She packed three items: a map, a flashlight, and water.”

Exam Focus

• Why it matters: ACT loves “punctuation-only” questions where clause knowledge is the whole game.
• Typical question patterns:
  • Choose between comma/semicolon/period.
  • Decide if a colon is valid (must follow a complete sentence).
• Common mistakes:
  • Using a colon after a fragment (“such as:” is a common trap).
  • Using a comma where a semicolon/period is required.

Apostrophes and Possessives

An apostrophe most commonly shows possession or forms contractions.

Possessives

• Singular: “the student’s desk”
• Plural ending in s: “the students’ desks”
• Plural not ending in s: “children’s books”

Its vs. it’s

• it’s = it is / it has
• its = possessive

Example

• Correct: “The dog wagged its tail because it’s excited.”

Exam Focus

• Why it matters: These are quick points—ACT tests them with minimal context.
• Typical question patterns:
  • Choose between its/it’s, their/there/they’re.
  • Fix singular/plural possession based on meaning.
• Common mistakes:
  • Using an apostrophe for a plural (no possession).
  • Confusing its and it’s.

Dashes and Parentheses

Dashes and parentheses set off extra (often nonessential) information.

Dashes (—)

• Emphasize an interruption or aside.
• Must be used in matching pairs if they open and close an insertion.

Parentheses ( )

• De-emphasize supplementary information.
• Avoid stacking with other punctuation awkwardly.

Example

• “The final step—checking your work—prevents careless errors.”

Exam Focus

• Why it matters: ACT asks you to pick punctuation that matches tone and grammar without creating fragments.
• Typical question patterns:
  • Choose between commas, dashes, parentheses.
  • Fix mismatched punctuation (one dash instead of two).
• Common mistakes:
  • Using a dash on one side and a comma on the other.
  • Removing needed commas around nonessential information.

Subject-Verb Agreement

Subject-verb agreement means the verb matches the subject in number (singular/plural).

High-yield traps

• Intervening phrases: “The bouquet of roses is…” (subject = bouquet)
• Indefinite pronouns: some are singular (each, either, neither), some plural (many), some depend on context (some, all).
• Compound subjects: usually plural with “and,” but singular when treated as one unit (“peanut butter and jelly is my favorite”).

Example

• “Each of the players was ready.”

Exam Focus

• Why it matters: ACT embeds agreement errors inside long noun phrases to test whether you can locate the true subject.
• Typical question patterns:
  • Pick between is/are, has/have, was/were.
  • Fix agreement when a prepositional phrase intervenes.
• Common mistakes:
  • Matching the verb to the nearest noun instead of the subject.
  • Missing that “each/every” is usually singular.

Pronoun-Antecedent Agreement

A pronoun must agree with its antecedent (the word it replaces) in number (and, when relevant, gender).

Key situations

• Indefinite antecedents: “Everyone should bring his or her / their…” (ACT typically favors clear agreement; if plural “they/their” creates mismatch, revise the noun: “All students should bring their…”)
• Compound antecedents with “or/nor”: match the pronoun to the closer antecedent (often tested).

Example

• Better revision: “All participants should bring their ID.” (plural antecedent avoids mismatch)

Exam Focus

• Why it matters: Agreement is tested both as grammar and as clarity—ACT rewards clean rewrites.
• Typical question patterns:
  • Choose between his/their/its based on antecedent.
  • Replace a singular noun with a plural to fix agreement.
• Common mistakes:
  • Using “they” for a clearly singular antecedent without revising the antecedent.
  • Vague antecedents (“this,” “that,” “which”) with no clear noun.

Pronoun Case and Reference

Pronoun case means choosing subjective (I, he, she, we, they), objective (me, him, her, us, them), or possessive (my, his, their).

Case quick rules

• Subject position: “She and I are ready.”
• Object position: “The coach called her and me.”
• After prepositions: “between you and me”

Reference (clarity)

A pronoun must clearly point to one specific antecedent.

Example

• Unclear: “When Maya met Anna, she smiled.” (Who?)
• Clear: “Maya smiled when she met Anna.”

Exam Focus

• Why it matters: ACT tests case in compound structures (“X and I/me”) and tests whether pronouns create ambiguity.
• Typical question patterns:
  • Choose I/me, who/whom in a sentence role.
  • Fix “this/which/it” when the antecedent is unclear.
• Common mistakes:
  • Using “I” everywhere in a compound (“to Sam and I”).
  • Leaving “which/this” to refer to an entire vague idea.

Verb Tense and Tense Consistency

Verb tense indicates time; consistency means you don’t shift tenses without a reason.

Common ACT expectations

• Keep the dominant tense of the passage unless context demands change.
• Use past perfect (had + past participle) when showing an earlier past event relative to another past event.

Example

• Consistent past: “She walked to the store and bought milk.”
• Earlier past: “She had left before the call arrived.”

Exam Focus

• Why it matters: ACT passages often narrate events; tense errors disrupt timeline and clarity.
• Typical question patterns:
  • Choose among walks/walked/has walked/had walked.
  • Fix an unnecessary tense shift in a paragraph.
• Common mistakes:
  • Switching to present tense mid-story without a signal.
  • Overusing perfect tenses when simple past works.

Adjective and Adverb Usage

Adjectives modify nouns; adverbs modify verbs, adjectives, or other adverbs.

High-yield distinctions

• Good (adj) vs. well (adv): “She sings well.” / “She is good at singing.”
• Comparative forms:
  • Two things: -er / more (better, faster, more interesting)
  • Three+ things: -est / most

Example

• Wrong: “He did good on the test.”
• Right: “He did well on the test.”

Exam Focus

• Why it matters: These are quick grammar points that show up as single-word swaps.
• Typical question patterns:
  • Choose good/well, real/really.
  • Fix faulty comparisons (“more better”).
• Common mistakes:
  • Using an adjective to modify a verb (“ran quick”).
  • Comparing an item to the wrong group (“taller than any student” vs. “any other student”).

Modifier Placement

A modifier is a word/phrase that describes something; it must be placed next to what it modifies.

Common modifier errors

• Misplaced modifier: modifier is too far from the target.
• Dangling modifier: modifier has no clear subject.

Example

• Dangling: “Walking to the park, the rain started.”
• Fix: “Walking to the park, I noticed the rain starting.”

Exam Focus

• Why it matters: ACT tests clarity—modifier errors often create unintended (sometimes funny) meanings.
• Typical question patterns:
  • Rearrange phrases to make the subject clear.
  • Fix an opening -ing phrase so it modifies the right noun.
• Common mistakes:
  • Leaving an introductory phrase with no logical doer.
  • Placing “only” in the wrong spot (changes meaning).

Idiomatic Expressions and Preposition Usage

Idioms are standard word pairings in English; on the ACT, the “right” answer is the most conventional and clear.

Preposition and idiom examples

• agree with a person / agree to a plan
• responsible for, different from/than (usage varies; ACT tends to prefer the most common standard form)
• between (two) vs. among (three+)

Strategy

• Prefer concise, standard phrasing.
• Avoid answers that add words without improving meaning.

Example

• Better: “She is capable of solving the problem.”

Exam Focus

• Why it matters: Idioms can’t always be “logic’d out,” so ACT uses them to test familiarity with standard written English.
• Typical question patterns:
  • Choose the correct preposition (of/for/to/with).
  • Remove wordy or nonstandard phrasing.
• Common mistakes:
  • Picking a preposition that “sounds okay” but isn’t idiomatic.
  • Changing wording that was already standard (unnecessary edits).

Quick Review Checklist

• Can you identify whether a clause is independent or dependent?
• Can you fix a run-on using a period, semicolon, or comma + FANBOYS?
• Can you spot and repair a fragment (especially starting with because/which/although)?
• Can you make list items and paired structures perfectly parallel?
• Do you know when commas vs. semicolons vs. colons are valid?
• Can you form correct possessives (including its vs. it’s)?
• Can you match verbs to the true subject (ignoring intervening phrases)?
• Can you ensure pronouns agree with and clearly refer to an antecedent?
• Can you keep verb tenses consistent and logical in a passage?
• Can you fix misplaced/dangling modifiers and choose standard idiomatic prepositions?

Final Exam Pitfalls

1. Choosing punctuation before checking clauses: First decide if both sides can stand alone; then pick comma+FANBOYS, semicolon, or period.
2. “Nearest noun” agreement: Ignore prepositional phrases (“of…,” “along with…”)—make the verb match the real subject.
3. Letting pronouns go vague: If “this/which/it/they” could point to more than one noun, rewrite to name the antecedent.
4. Breaking parallel structure while fixing one word: When you change one list item, re-check the whole series and any paired construction.
5. Dangling opening modifiers: Ensure the noun right after the comma is the doer described by the introductory phrase.

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Claude Opus 4.6

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What You Need to Know

• Conventions of Standard English make up roughly 51–56% of the ACT English test (approximately 38–40 of the 75 questions). Mastering grammar, punctuation, and sentence structure is the single highest-yield investment you can make for this section.
• The ACT tests grammar in context — you'll read passages and choose the best revision from four answer choices. The correct answer is almost always the most concise, grammatically correct option.
• Most questions fall into predictable patterns: fixing run-ons, correcting agreement errors, choosing proper punctuation, and ensuring clear modifier/pronoun references. Learn the rules, and you'll spot the errors quickly.
• When in doubt, the shortest answer that is grammatically complete and clear is often correct. Wordiness is a trap on the ACT.

Sentence Structure and Formation

Sentence structure refers to how clauses and phrases are arranged to form complete, logical sentences. A grammatically correct sentence requires at least one independent clause — a subject + verb combination that expresses a complete thought.

Key building blocks:

• Independent clause: Can stand alone. The dog barked.
• Dependent (subordinate) clause: Cannot stand alone; starts with a subordinating conjunction or relative pronoun. Because the dog barked…
• Phrase: A group of words lacking a subject-verb pair. Running through the park…

Run-On Sentences and Comma Splices

A run-on sentence (fused sentence) joins two independent clauses with no punctuation or conjunction. A comma splice joins them with only a comma.

Correct fixes: She studied hard; she passed the test. / She studied hard, and she passed the test.

Sentence Fragments

A sentence fragment is a group of words punctuated as a sentence but missing a subject, a verb, or a complete thought.

• Fragment: Running through the park on Saturday. (no subject or main verb)
• Fix: She was running through the park on Saturday.

On the ACT, fragments often appear as dependent clauses standing alone — look for words like because, although, which, that starting an "answer" that has no independent clause attached.

Exam Focus

• Why it matters: Sentence boundary errors appear in nearly every ACT English passage.
• Typical question patterns: You're asked to choose the correct way to join or separate two clauses; one answer is a run-on, one is a fragment, and the correct choice uses proper punctuation/conjunction.
• Common mistakes: Choosing a comma splice because it "sounds right"; failing to recognize a subordinate clause as a fragment.

Parallel Structure

Parallel structure means items in a list or comparison use the same grammatical form.

• Wrong: She likes hiking, swimming, and to bike.
• Right: She likes hiking, swimming, and biking.

Parallelism applies to lists, comparisons (more… than…), and correlative conjunctions (both…and, either…or, not only…but also).

Exam Focus

• Why it matters: Tested 1–3 times per test; easy points once you know the rule.
• Typical question patterns: A sentence with a series of actions or items where one element breaks the pattern.
• Common mistakes: Not checking every item in the list; missing parallelism in two-part comparisons.

Coordination and Subordination

Coordination links equally important ideas with coordinating conjunctions (FANBOYS: for, and, nor, but, or, yet, so) or semicolons. Subordination makes one idea dependent on another using subordinating conjunctions (because, although, since, when, while, if).

The ACT tests whether you choose the logical connector. Although signals contrast; because signals cause.

Exam Focus

• Why it matters: Tests logical relationships — a grammar rule and a reasoning skill combined.
• Typical question patterns: Choose between however, therefore, because, or although to connect two clauses.
• Common mistakes: Picking a transition that sounds formal but reverses the intended meaning.

Commas, Semicolons, and Colons

Commas

Use commas to:

1. Separate items in a list of three or more
2. Set off nonessential (nonrestrictive) information: My brother, who lives in Texas, is visiting.
3. Follow an introductory element: After the game, we went home.
4. Separate two independent clauses joined by a FANBOYS conjunction

Do not use a comma between a subject and its verb or between a verb and its object.

Semicolons

Use a semicolon to:

• Join two related independent clauses without a conjunction: She studied; she passed.
• Separate items in a list that already contains commas

Colons

Use a colon after an independent clause to introduce a list, explanation, or elaboration. The clause before the colon must be independent.

• Right: She bought three things: eggs, milk, and bread.
• Wrong: She bought: eggs, milk, and bread. ("She bought" is not a complete clause here in standard usage; the ACT prefers the full clause before a colon.)

Exam Focus

• Why it matters: Punctuation questions are the most frequently tested convention on the ACT English section.
• Typical question patterns: Four choices with different comma placements; choosing between a comma, semicolon, colon, or no punctuation.
• Common mistakes: Adding unnecessary commas (especially between subject and verb); confusing semicolon and colon usage.

Apostrophes and Possessives

• Singular possessive: the dog's bone
• Plural possessive: the dogs' bones
• Its vs. it's: its = possessive; it's = it is / it has
• Who's vs. whose: who's = who is; whose = possessive

Apostrophes are never used to form simple plurals.

Exam Focus

• Why it matters: Tested 2–3 times per test; quick to answer if you know the rules.
• Typical question patterns: Choosing between its/it's, their/they're/there, or singular vs. plural possessives.
• Common mistakes: Using it's as a possessive; adding apostrophes to plural nouns that aren't possessive.

Dashes and Parentheses

Em dashes (—) and parentheses set off nonessential information. Dashes add emphasis; parentheses de-emphasize.

• Key rule: Dashes come in pairs when the nonessential information is mid-sentence — just like parentheses. If you open with a dash, close with a dash (not a comma).

Exam Focus

• Why it matters: The ACT frequently tests whether students can match paired punctuation.
• Typical question patterns: A sentence with an opening dash — you must choose the answer that closes with a dash rather than a comma or parenthesis.
• Common mistakes: Mixing a dash on one side with a comma on the other.

Subject-Verb Agreement

The verb must agree in number with its subject, not with nearby nouns.

• The box of chocolates is on the table. (subject = box, singular)
• Watch for inverted sentences: Here are the results.
• Compound subjects joined by and → plural. Subjects joined by or/nor → verb matches the closer subject.

Exam Focus

• Why it matters: Tested 2–4 times per test; the ACT deliberately places distracting prepositional phrases between subject and verb.
• Typical question patterns: A long prepositional phrase separates the subject from the verb; you choose singular vs. plural verb.
• Common mistakes: Making the verb agree with the nearest noun rather than the actual subject.

Pronoun-Antecedent Agreement

A pronoun must agree in number and person with its antecedent (the noun it replaces).

• Each student must bring his or her book. ("each" is singular)
• Collective nouns (team, group) are typically singular on the ACT.

Pronoun Case and Reference

Pronoun case: Use subjective (I, he, she, we, they, who) for subjects and objective (me, him, her, us, them, whom) for objects. Tip: Remove the other person from the sentence to test — "gave it to Sarah and me" → "gave it to me" ✓.

Pronoun reference: Every pronoun must refer to one clear antecedent. Ambiguous reference — where a pronoun could refer to more than one noun — is always wrong on the ACT.

Exam Focus

• Why it matters: Pronoun questions appear in almost every passage.
• Typical question patterns: Choosing between who/whom, I/me, or replacing an ambiguous pronoun with the specific noun.
• Common mistakes: Using who when whom is correct (and vice versa); leaving ambiguous pronoun references.

Verb Tense and Tense Consistency

Use context clues (dates, time words, surrounding verb tenses) to determine the correct tense. The ACT primarily tests:

• Simple past vs. past perfect (had + past participle for the earlier of two past events)
• Present vs. past consistency within a passage
• Maintaining tense consistency — don't shift tenses without a reason

Exam Focus

• Why it matters: Tense errors appear 2–3 times per test.
• Typical question patterns: Choosing the correct verb form to match the passage's established time frame; identifying an unnecessary tense shift.
• Common mistakes: Switching from past to present tense mid-paragraph; overusing past perfect when simple past is sufficient.

Adjective and Adverb Usage

Adjectives modify nouns; adverbs modify verbs, adjectives, or other adverbs.

• Wrong: She ran quick. → Right: She ran quickly.
• After linking verbs (is, seems, feels), use an adjective: She feels bad (not badly).

Exam Focus

• Why it matters: Tested occasionally; easy points.
• Typical question patterns: Choosing between an adjective and adverb form.
• Common mistakes: Using good instead of well after action verbs; using badly after linking verbs.

Modifier Placement

A modifier should be placed as close as possible to the word it describes.

• Dangling modifier: Walking to school, the rain started. (The rain wasn't walking.)
• Fix: Walking to school, I got caught in the rain.
• Misplaced modifier: She almost drove her kids to school every day. → She drove her kids to school almost every day.

Exam Focus

• Why it matters: Dangling and misplaced modifiers appear 1–2 times per test.
• Typical question patterns: An introductory participial phrase followed by answer choices that change the subject of the main clause — you must pick the subject that logically performs the action.
• Common mistakes: Ignoring who is actually performing the action described by the opening phrase.

Idiomatic Expressions and Preposition Usage

Idioms are conventional word combinations that must simply be memorized — there's no grammar rule that explains them.

Common ACT-tested idioms:

Exam Focus

• Why it matters: A few questions per test rely purely on knowing the right preposition.
• Typical question patterns: Four answer choices that are identical except for the preposition.
• Common mistakes: Choosing the preposition that "sounds right" based on casual speech rather than standard written English.

Quick Review Checklist

• ☐ Can you identify and fix run-on sentences, comma splices, and fragments?
• ☐ Do you know when to use a comma, semicolon, colon, or dash?
• ☐ Can you spot subject-verb agreement errors when a prepositional phrase separates the subject and verb?
• ☐ Do you know the difference between its/it's, who's/whose, and their/they're/there?
• ☐ Can you correct a dangling or misplaced modifier by identifying the logical subject?
• ☐ Do you know how to maintain parallel structure in a list or comparison?
• ☐ Can you choose the correct pronoun case (who vs. whom, I vs. me)?
• ☐ Do you know how to maintain verb tense consistency and when past perfect is required?
• ☐ Can you identify an ambiguous pronoun reference and replace it with the correct noun?
• ☐ Do you know common ACT-tested idiomatic prepositions (different from, interested in, etc.)?

Final Exam Pitfalls

1. Choosing a comma splice because it "sounds natural." Two independent clauses need more than a comma — use a semicolon, a period, or a comma + FANBOYS conjunction.
2. Making the verb agree with the wrong noun. Cross out prepositional phrases between the subject and verb to find the true subject. The list of items is long — not are.
3. Mixing paired punctuation. If a nonessential clause opens with a dash, it must close with a dash — not a comma or parenthesis. The same applies to parentheses.
4. Shifting verb tenses without reason. If a passage is written in past tense, don't switch to present tense unless the context clearly demands it.
5. Using it's as a possessive. Remember: it's always means it is or it has. The possessive form has no apostrophe: its.
6. Ignoring the logical subject after an introductory modifier. The noun immediately after the comma must be the one performing the action. Covered in mud, the dog needed a bath — not Covered in mud, a bath was needed.