Sentence Structure

American Diploma › ACT English and Reading — Complete Course

What this question type tests

Sentence-structure questions belong to the Conventions of Standard English reporting category of the ACT English test. On the enhanced ACT this category is 38–43% of the English score, together with punctuation and usage. The English test has 50 questions (40 scored) in 35 minutes — about 42 seconds per question — spread over five essays: three of about 340 words with 10 questions each and two of about 185 words with 5 questions each.

You will not see a question like "Find the fragment." Instead, a part of the essay is underlined and numbered. Next to it are four versions of that part, and the first choice is usually NO CHANGE. Most sentence-structure items have no question stem at all: you simply pick the version that makes a correct, clear sentence. Sometimes a stem appears, such as "Which choice is NOT acceptable?" — read it carefully, because then you are looking for the one WRONG version.

This page covers seven problems that the ACT tests again and again: fragments, run-ons and comma splices, joining clauses, misplaced and dangling modifiers, parallelism, faulty comparisons, and shifts in point of view and verb tense. Learn the rule, then the trap, then practise.

Rule 1: Every sentence needs a subject and a main verb (fragments)

A fragment is a group of words that starts with a capital letter and ends with a period but is not a complete sentence. A complete sentence needs a subject, a main (finite) verb, and a complete thought. The ACT builds fragments in four ways:

Quick test: cross out everything between commas and any who/which/that clause. Is there still a subject and a verb that could stand alone? If not, it is a fragment.

Rule 2: Run-ons and comma splices

An independent clause can stand alone as a sentence. When you put two of them together, you must join them correctly. Two common mistakes:

• Run-on (fused sentence) — no punctuation at all. ✗ The museum opened in 2004 it now has two million objects.
• Comma splice — only a comma. ✗ The museum opened in 2004, it now has two million objects.

Watch for second clauses that begin with it, this, they, he, she, there — these words start a new independent clause, so a comma alone is never enough before them. In contrast, which and who start dependent clauses, so a comma is fine: ✓ The museum opened in 2004, which makes it one of the newest in the city.

Rule 3: The correct ways to join clauses

The teacher's rule for the semicolon: it joins two independent clauses that are closely related — both sides must be complete sentences. If you could not put a period there, you cannot put a semicolon there. (SAT/ACT extra rule: a semicolon may also separate list items that already contain commas, e.g. "Cairo, Egypt; Rabat, Morocco; and Tunis, Tunisia." This is the only other use.)

Conjunctive adverbs — however, therefore, still, instead, as a result, moreover, consequently, otherwise — are not FANBOYS. They cannot join two clauses with only a comma.

• ✗ The road was closed, therefore, we walked.
• ✓ The road was closed; therefore, we walked.
• ✓ The road was closed, so we walked.
• ✓ We, therefore, walked. (one clause — the adverb is just extra information inside a pair of commas)

Rule 4: Modifiers go next to what they describe

A modifier is a word or phrase that describes something. On the ACT it must sit as close as possible to the thing it describes.

Dangling modifier. An opening phrase (often -ing, -ed, or "As a…") describes the subject that comes right after the comma. If that subject is the wrong thing, the modifier dangles.

• ✗ Walking along the beach, the shells looked beautiful. (the shells were not walking)
• ✓ Walking along the beach, Nadia thought the shells looked beautiful.
• ✗ Built in the 1920s, visitors still admire the theatre. (the visitors were not built)
• ✓ Built in the 1920s, the theatre is still admired by visitors.
• ✗ As a young engineer, the bridge design was Hoda's first big project.
• ✓ As a young engineer, Hoda designed her first big project: a bridge.

Possessive trap: "Walking along the beach, Nadia's phone rang." Nadia's phone was not walking. The subject is "phone," not Nadia. The ACT loves this trap.

Misplaced modifier. A word such as only, nearly, almost, just, even changes meaning depending on where it sits. A phrase can also be placed so that it seems to describe the wrong noun.

• ✗ She almost read the whole book. (she did not start?)
• ✓ She read almost the whole book.
• ✗ The chef served soup to the guests in plastic bowls that was cold.
• ✓ The chef served cold soup to the guests in plastic bowls.

Rule 5: Parallelism — items in a series must match

When a sentence lists two or more items, or uses a pair such as not only … but also, either … or, neither … nor, both … and, whether … or, every item must have the same grammatical form.

• ✗ The club teaches students to code, design games, and how to present them.
• ✓ The club teaches students to code, design games, and present them.
• ✗ The library is popular not only for its books but also because it is quiet.
• ✓ The library is popular not only for its books but also for its quiet rooms.
• ✗ She prefers swimming to run.
• ✓ She prefers swimming to running.

Method: find the first item, note its form (to + verb? -ing? noun? adjective? for + noun?), and make every other item copy it.

Rule 6: Faulty comparisons — compare like with like

A comparison must compare two things of the same kind: a city with a city, a population with a population, a person's work with another person's work.

• ✗ The population of Alexandria is smaller than Cairo. (population vs city)
• ✓ The population of Alexandria is smaller than that of Cairo.
• ✓ Alexandria's population is smaller than Cairo's.
• ✗ Like many birds, the falcon's eyesight is excellent. (birds vs eyesight)
• ✓ Like many birds, the falcon has excellent eyesight.
• ✗ Her essay was longer than any student in the class. (essay vs student; and she is in the class)
• ✓ Her essay was longer than that of any other student in the class.

Also check the words: than (comparison) vs then (time); fewer for countable things, less for amounts; between two, among three or more; -er/more for two things, -est/most for three or more.

Rule 7: No unnecessary shifts in point of view or verb tense

Point of view (pronoun shifts). If a sentence or paragraph starts with "one," "a student," or "people," it should not suddenly switch to "you" or "we."

• ✗ When a visitor enters the temple, you notice the painted ceiling.
• ✓ When a visitor enters the temple, he or she notices the painted ceiling.
• ✓ When visitors enter the temple, they notice the painted ceiling.

Verb tense. Keep the same time frame unless the meaning really changes. Look for time clues: dates, "last year," "today," "since," "by the time." Also match the tense of the verbs around the underlined part.

• ✗ In 1952, the family moved to Aswan and opens a small bakery.
• ✓ In 1952, the family moved to Aswan and opened a small bakery.
• ✓ The bakery opened in 1952 and still sells bread today. (a real change in time: past → present)
• ✗ By the time the guests arrived, the children already ate the cake.
• ✓ By the time the guests arrived, the children had already eaten the cake. (past perfect — had + past participle — for the earlier of two past actions)

A 4-step method for every sentence-structure item

1. Read the whole sentence — and the sentence before it if the underline is at the start. Many errors only appear when you see the full sentence.
2. Spot what changes in the choices. Commas → semicolons? -ing → past tense? Word order? The difference between the choices tells you the rule being tested.
3. Apply the rule: find subjects and verbs, count the independent clauses, check what each modifier touches, line up the list items, check the comparison and the time frame.
4. Plug your answer back in and read the sentence once more. If two choices still seem correct, choose the one that is clearer and shorter — but never the shorter one if it breaks a rule.

Worked examples

Worked example 1 — comma splice

Passage: The Siwa Oasis lies far from any large city. For centuries, travellers crossed the desert by camel to reach __it, the journey took__ several weeks.

Choose the best version of the underlined portion.

• A) NO CHANGE
• B) it; the journey took
• C) it, the journey taking took
• D) it the journey took

Answer: B

• A) ✗ Wrong: Comma splice: "travellers crossed the desert…" and "the journey took several weeks" are both independent clauses joined only by a comma.
• B) ✓ Correct: A semicolon joins two closely related independent clauses.
• C) ✗ Wrong: Nonsense verb form ("taking took") — two verbs for one subject.
• D) ✗ Wrong: Run-on: two independent clauses with no punctuation.

Worked example 2 — dangling modifier (possessive trap)

Passage: __Trained as an architect in Cairo, Hassan Fathy's buildings__ used mud brick, an ancient material.

Choose the best version of the underlined portion.

• A) NO CHANGE
• B) Trained as an architect in Cairo, Hassan Fathy designed buildings that
• C) Hassan Fathy trained as an architect in Cairo, his buildings
• D) Having trained as an architect in Cairo, the buildings of Hassan Fathy

Answer: B

• A) ✗ Wrong: Possessive trap: the subject is "buildings," and buildings were not trained as architects.
• B) ✓ Correct: The person who trained (Hassan Fathy) comes right after the modifier, and "that used mud brick" correctly describes the buildings.
• C) ✗ Wrong: Comma splice: two independent clauses joined with a comma.
• D) ✗ Wrong: Still dangling: the buildings, not Fathy, follow the modifier.

Worked example 3 — parallelism

Passage: Volunteers at the turtle centre clean the tanks, feed the young turtles, and __they are also recording__ each animal's weight.

Choose the best version of the underlined portion.

• A) NO CHANGE
• B) also recording
• C) record
• D) to record

Answer: C

• A) ✗ Wrong: Breaks the list: two plain present verbs (clean, feed) then a new clause in a different form.
• B) ✗ Wrong: -ing form does not match clean and feed.
• C) ✓ Correct: Three matching present-tense verbs: clean, feed, record.
• D) ✗ Wrong: To + verb does not match the other two verbs.

Worked example 4 — faulty comparison and tense together

Passage: Last summer, the price of mangoes in the market __rises higher than bananas__.

Choose the best version of the underlined portion.

• A) NO CHANGE
• B) rose higher than bananas
• C) rises higher than that of bananas
• D) rose higher than that of bananas

Answer: D

• A) ✗ Wrong: Two errors: present tense with "last summer," and price compared with fruit.
• B) ✗ Wrong: Tense fixed, but the comparison is still price vs bananas.
• C) ✗ Wrong: Comparison fixed, but the tense is still wrong.
• D) ✓ Correct: Past tense matches "last summer," and "that of bananas" compares price with price. When two errors are tested, you need the choice that fixes both.

Worked example 5 — a NOT question

Passage: My grandmother never wrote down her __recipes. She kept__ them all in her head and cooked from memory every day.

Which of the following alternatives to the underlined portion would NOT be acceptable?

• A) recipes; she kept
• B) recipes: she kept
• C) recipes, she kept
• D) recipes. Instead, she kept

Answer: C

• A) ✓ Acceptable: A semicolon correctly joins two closely related independent clauses.
• B) ✓ Acceptable: The colon comes after a complete sentence, and the second clause explains the first (how she managed without writing).
• C) ✗ The answer: NOT acceptable: a comma alone between two independent clauses is a comma splice. On a NOT question, the error IS the answer.
• D) ✓ Acceptable: Two separate sentences, and "Instead" logically links not writing the recipes down with keeping them in her head.

Practice

Read the essay and answer the 12 questions. Each question refers to the numbered underlined portion. The questions mix all seven rules, just like the real test.

All pages in this course

Start here

• The Enhanced ACT: Complete Overview
• How to Attack ACT English

English: Conventions of Standard English

• ACT Punctuation
• ACT Grammar and Usage
• Sentence Structure

English: Production of Writing and Knowledge of Language

• Concision and Redundancy
• Relevance: Add, Delete and Writer's Goal
• Organisation: Order and Transitions
• Word Choice and Tone

Reading

• ACT Reading Strategy: Read Fast, Answer Smart
• Key Ideas and Details
• Craft and Structure
• Integration of Knowledge and Ideas

Practice tests

• ACT English — Practice Test 1
• ACT English — Practice Test 2
• ACT Reading — Practice Test 1
• ACT Reading — Practice Test 2