My brother, who lives in Denver, works as a software engineer.
NO CHANGE. The clause "who lives in Denver" is nonrestrictive — it adds extra information but isn't essential to identify which brother. Nonrestrictive clauses are set off by commas on both sides.
If you only have one brother, "who lives in Denver" is extra info → commas. If you have multiple brothers and need to specify which one, it would be restrictive → no commas: "My brother who lives in Denver works as..."
The experiment yielded surprising results**;** the researchers decided to run additional trials.
NO CHANGE. Two independent clauses joined by a semicolon is correct. Common wrong answers on the ACT:
Rule: If both sides of the punctuation can stand alone as sentences, you need a semicolon, a period, or a comma + coordinating conjunction (FANBOYS).
The recipe requires three key spices**:** cumin, paprika, and turmeric.
NO CHANGE. A colon follows an independent clause and introduces a list, explanation, or elaboration. The part before the colon must be a complete sentence.
Wrong: "The three key spices are**:** cumin, paprika, and turmeric." — "The three key spices are" is not a complete sentence (it needs a complement), so a colon is wrong here. Correct: "The three key spices are cumin, paprika, and turmeric."
The company's new policy requires all employees to complete training.
NO CHANGE. Singular possessive: company → company's. Common ACT traps:
| Form | Meaning |
|---|---|
| company's | belonging to one company |
| companies' | belonging to multiple companies |
| companies | plural, no possession |
| it's | it is / it has |
| its | belonging to it |
"Its" vs. "it's" appears on almost every ACT. If you can replace the word with "it is," use "it's." Otherwise, use "its."
Because the funding was cut short. The project had to be scaled back.
This is a fragment followed by a sentence. "Because the funding was cut short" is a dependent clause — it cannot stand alone. Fix options:
On the ACT, the underlined portion will usually be the punctuation between the two parts, and the correct answer joins them.
The museum opened its new wing last month visitors have been lining up since then.
This is a run-on (fused sentence). Two independent clauses with no punctuation or conjunction. Correct fixes:
The ACT will offer these as choices. "Last month, visitors" (comma only) is a comma splice and is wrong.