In the verified TTA maize question, the correct punctuation is a comma after mexicana, not a colon. The phrase that follows renames mexicana, so it functions as a nonessential appositive and needs closing punctuation. A colon would break the sentence because the words before it do not create the required complete setup for an explanation.
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Question banks: October 2026 English question bank
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The rule this SAT question tests
An appositive is a noun or noun phrase that renames a nearby noun. In the sentence "Maya, the team captain, spoke first," the phrase "the team captain" renames Maya. You can remove that phrase and still have a complete sentence: "Maya spoke first." Because the extra identification is nonessential, commas set it off.
The same test works when the appositive appears near the end of a sentence. Read the sentence without the renaming phrase. If the grammar and core meaning still hold, treat the phrase as nonessential and use the punctuation needed to open or close it.
The TTA maize example
TTA passage 101433 discusses maize and a second subspecies of teosinte. The blank comes immediately before a phrase identifying that subspecies as mexicana, followed by the description "a highland ancestor." Question 576242 asks which choice follows Standard English conventions.
The TTA database marks choice record 576243, "mexicana," as correct. Inserted into the sentence, the structure becomes:
That second subspecies was mexicana, a highland ancestor.
The sentence is complete at "That second subspecies was mexicana." The phrase "a highland ancestor" then renames or describes mexicana. The comma marks the beginning of that nonessential appositive.
Why the colon choices fail
A colon introduces a list, explanation, example, or restatement after a complete independent clause. Test the words before the proposed colon by themselves. "That second subspecies was mexicana" is complete, but placing the colon directly after mexicana would make the following phrase feel like an announced explanation rather than a grammatical renaming phrase. The TTA key confirms that the comma is the intended answer for this item.
A semicolon also fails. A semicolon normally joins two independent clauses. "A highland ancestor" has no subject-verb pair, so it cannot stand as the second clause. Leaving out punctuation fails because the descriptive phrase needs a boundary.
A fast way to test appositives
- Find the noun that appears immediately before the descriptive phrase.
- Ask whether the following noun phrase renames the same person, place, thing, or idea.
- Remove the renaming phrase and read the sentence again.
- If the sentence remains complete and keeps its core meaning, punctuate the nonessential phrase.
- Check both boundaries when the phrase sits in the middle of the sentence.
Do not choose punctuation because it creates a longer pause when you read aloud. SAT punctuation follows sentence structure. The deletion test gives you a grammatical reason for your answer.
Appositive or essential information?
Some noun phrases identify which person or thing the writer means. In "The poet Ada Limón wrote the poem," the name may be essential because it tells you which poet. In "Ada Limón, the poet laureate, spoke," the descriptive phrase is extra information and takes commas. The surrounding context decides whether the name or description is essential.
That distinction matters more than the word itself. A person's name can be essential in one sentence and nonessential in another. Read the sentence as a complete unit before touching the answer choices.
Practice the rule
Work through the free Extra Information: Commas, Dashes and Parentheses lesson notes. For each item, delete the suspected appositive and check whether the base sentence remains complete.
Then compare the boundary with the rule in Semicolon vs. Period on the SAT. That guide helps you separate complete-clause punctuation from punctuation used around phrases.
When you are ready to apply both rules together, take the free SAT punctuation test. Create a free account if you want to save your progress and return to the test later.
Frequently asked questions
What is an appositive on the SAT?
An appositive is a noun or noun phrase that renames a nearby noun. Nonessential appositives need punctuation that separates them from the main sentence.
Why is "mexicana," correct in the maize question?
The following phrase, "a highland ancestor," renames or describes mexicana. The comma opens that nonessential appositive.
When can the SAT use a colon?
A colon can introduce a list, explanation, example, or restatement after a complete independent clause. It does not replace punctuation required around a nonessential phrase.
Frequently Asked Questions
What is an appositive on the SAT?
An appositive is a noun or noun phrase that renames a nearby noun. Nonessential appositives need punctuation that separates them from the main sentence.
Why is mexicana followed by a comma in the maize question?
The following phrase, a highland ancestor, renames or describes mexicana. The comma opens that nonessential appositive.
When can the SAT use a colon?
A colon can introduce a list, explanation, example, or restatement after a complete independent clause.