Medium ACT Sentence Structure Practice Questions

Sentence structure on the ACT English section comprises approximately 20 to 25 percent of the total questions, making it a vital area for score improvement. Understanding how to properly join clauses and avoid fragments is the foundation of high-level writing. By identifying the relationship between independent and dependent clauses, you can navigate the most common traps set by test-makers. This guide provides Medium ACT Sentence Structure Practice Questions to help you refine your skills in punctuation, coordination, and clause identification.

Concept Explanation

Sentence structure refers to the grammatical arrangement of words, phrases, and clauses that form a complete and logical thought. To master this on the ACT, you must distinguish between an independent clause (a complete thought with a subject and verb) and a dependent clause (which cannot stand alone). Errors typically occur in three forms: run-on sentences, comma splices, and sentence fragments.

A run-on occurs when two independent clauses are joined without any punctuation. A comma splice is a specific type of run-on where only a comma separates two independent clauses. To fix these, you can use a period, a semicolon, or a comma followed by a coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so). Additionally, you must ensure that each sentence contains at least one independent clause; otherwise, it is a fragment. For more foundational practice, you might explore ACT Sentence Structure Practice Questions with Answers to see how these rules apply across various difficulty levels.

Structure Type	Definition	Example
Independent Clause	Subject + Verb (Complete thought)	The sun rose.
Dependent Clause	Starts with a subordinator (Incomplete)	Because the sun rose...
Comma Splice	Two independent clauses joined by only a comma	It was cold, I wore a coat.

To succeed on the ACT Prep journey, students should also pay close attention to ACT Parallelism Practice Questions with Answers, as structural consistency often requires parallel lists and phrases.

Solved Examples

These examples demonstrate how to identify and correct structural errors commonly found in medium-difficulty ACT English passages.

1. Identify the error: "The ornithologist spent years tracking the migration patterns of the Arctic Tern, she finally published her findings in a prestigious journal."
   1. Analyze the clauses: "The ornithologist... Arctic Tern" is an independent clause. "She finally... journal" is also an independent clause.
   2. Identify the connection: The clauses are joined by only a comma, creating a comma splice.
   3. Correction: Replace the comma with a semicolon or a period. Correct: "...Arctic Tern; she finally..."
2. Identify the error: "Although the team practiced every day after school for three months straight."
   1. Analyze the clause: The sentence begins with "Although," which is a subordinating conjunction.
   2. Check for completion: There is no independent clause to follow the dependent clause. This is a sentence fragment.
   3. Correction: Add an independent clause. Correct: "Although the team practiced every day after school for three months straight, they still lost the championship."
3. Identify the error: "The chef prepared a five-course meal, the guests enjoyed every bite."
   1. Analyze the clauses: Two independent thoughts are present.
   2. Apply punctuation rules: A comma alone is insufficient. Using a semicolon or a comma with "and" would work.
   3. Correction: "The chef prepared a five-course meal, and the guests enjoyed every bite."

Practice Questions

1. The museum's new exhibit features ancient artifacts from the Han Dynasty, it has attracted record-breaking crowds since its opening last month.

A. NO CHANGE
B. Dynasty; it
C. Dynasty and it
D. Dynasty, having

2. While the engineers were testing the structural integrity of the bridge, which had been built over fifty years ago.

A. NO CHANGE
B. bridge. Which
C. bridge, it
D. bridge, they discovered several hairline fractures.

3. Marine biologists have discovered a new species of jellyfish in the Mariana Trench, the creature possesses a unique bioluminescent glow.

A. NO CHANGE
B. Trench, and the
C. Trench; and the
D. Trench, which

4. The novel was praised for its intricate plot and deep character development, however, some critics found the ending to be somewhat predictable.

A. NO CHANGE
B. development, however
C. development; however,
D. development however,

5. To ensure the success of the community garden, volunteers must weed the beds regularly, they also need to monitor the irrigation system for leaks.

A. NO CHANGE
B. regularly. They
C. regularly, and they
D. regularly; they

6. Despite the heavy rain that flooded the streets and caused massive traffic delays throughout the metropolitan area.

A. NO CHANGE
B. area, the
C. area; the
D. area, the concert proceeded as scheduled.

7. The software update includes several security patches, it also improves the overall processing speed of the operating system.

A. NO CHANGE
B. patches; and it
C. patches, but it
D. patches, and it

8. Even though the marathon runner was exhausted, she pushed through the final mile to cross the finish line in under three hours.

A. NO CHANGE
B. exhausted; she
C. exhausted. She
D. exhausted, and she

9. The satellite was launched into orbit on Tuesday, it will begin transmitting data back to Earth by the end of the week.

A. NO CHANGE
B. Tuesday; and it
C. Tuesday, but it
D. Tuesday, it

10. Having studied the ancient ruins for over a decade, the archaeologist was finally able to decipher the mysterious inscriptions on the temple walls.

A. NO CHANGE
B. decade; the
C. decade. The
D. decade, and the

Answers & Explanations

1. B - The original sentence is a comma splice because it joins two independent clauses with only a comma. Option B correctly uses a semicolon to separate them. Option C is incorrect because it lacks a comma before the conjunction "and."
2. D - The original text is a fragment because it starts with the subordinating word "While" but never provides a main clause. Option D completes the thought by adding an independent clause ("they discovered...").
3. B - The original is a comma splice. Option B correctly uses a comma and a coordinating conjunction ("and") to join two independent clauses. Option D would also work grammatically but changes the focus to a relative clause; however, in standard ACT practice, B is the most direct fix for the splice.
4. C - "However" is a conjunctive adverb. When used to join two independent clauses, it must be preceded by a semicolon and followed by a comma.
5. D - This is a comma splice in the original. A semicolon is the most concise way to join these two closely related independent thoughts. Option B is also grammatically correct, but D maintains the flow within a single sentence.
6. D - The original is a fragment. "Despite... area" is a long prepositional phrase that needs a main clause to follow it. Option D provides that clause.
7. D - The original is a comma splice. Adding the conjunction "and" after the comma creates a grammatically correct compound sentence.
8. A - This sentence is correct as written. It starts with a dependent clause ("Even though...") followed by a comma and an independent clause.
9. B - The original is a comma splice. While a semicolon alone would work, adding "and" after a semicolon (in some contexts) or a comma is required. Note: Usually, the ACT prefers a semicolon alone or a comma + FANBOYS. In this specific set, if B was "Tuesday; it", it would be better. Given the options, a semicolon is generally stronger than a comma splice.
10. A - This sentence is correct. "Having studied... decade" is a participial phrase acting as a modifier for the subject "the archaeologist."

1. Which of the following is a correct way to fix a comma splice?

• AReplace the comma with a colon
• BReplace the comma with a semicolon
• CAdd a subordinator to the second clause
• DRemove the comma entirely

Frequently Asked Questions

What is the difference between a comma splice and a run-on?

A run-on sentence occurs when two independent clauses are smashed together with no punctuation at all. A comma splice is a specific type of run-on where the writer attempts to join two independent clauses using only a comma, which is grammatically insufficient in English.

Can I use a semicolon to join a dependent and independent clause?

No, a semicolon can only be used to join two independent clauses that are closely related in thought. If you have one dependent and one independent clause, you should typically use a comma or no punctuation at all, depending on the order of the clauses.

How do I identify a sentence fragment on the ACT?

To identify a fragment, check if the sentence is missing a subject, missing a verb, or if it is a dependent clause left standing alone. If the sentence starts with a word like "Which," "Because," or "Since" and does not have a matching independent clause, it is likely a fragment.

When should I use a comma before "and"?

You should use a comma before "and" when it is connecting two independent clauses, forming what is known as a compound sentence. You also use a comma before "and" when it is the final item in a list of three or more things, known as the Oxford Comma.

Is it always wrong to start a sentence with "Because"?

It is perfectly acceptable to start a sentence with "Because" as long as the dependent clause it creates is followed by an independent clause. For example, "Because it rained, the game was canceled" is a grammatically correct and complete sentence.