SAT — punctuation within a sentence

Where the companion material covers the boundary between one sentence and the next, these ten questions cover everything that happens inside a sentence: series, apostrophes, adjectives, colons, dashes and quotation marks. Seven of the sentences are faulty and three are correct as written, and knowing which is which is half the exercise — a reader convinced that every question hides an error will find errors that are not there.

Two questions are worth the time even for someone who punctuates well. One asks about a series of place names — Marlow, Ohio, Kenton, Vermont, and Ashby, Oregon — where the commas are doing two jobs at once and a reader genuinely cannot tell whether three places are named or six. Semicolons between the items and commas inside them settle it, and the explanation invites you to try the count first, because the ambiguity is easier to feel than to be told about. The other asks about "a rare, seventeenth-century manuscript" and gives the test that decides every question of this kind: reverse the two adjectives, then try joining them with "and". Both work in "a long, tedious meeting", so the comma belongs there. Neither works here, so it does not.

The question about "its" and "it's" is the one most often got wrong by people who know the rule perfectly, because the sentence uses both words and puts each in the other's place. Saying each aloud as "it is" resolves it in a second. And the quotation-mark question has a wrong answer worth knowing rather than merely discarding: it states the British convention, under which a period stays outside the closing mark unless it belongs to the quoted words themselves. That answer is correct in London and wrong on this test, which is a more useful thing to learn than a rule with no reason attached.

The three correct sentences each demonstrate something: a pair of commas enclosing an appositive, a colon introducing a single word for emphasis, and a dash gathering up a list into a summary. The explanation of the dash makes a point that applies across the whole domain — a colon would also have been acceptable in that position, and the question asks whether what the writer wrote is wrong, not whether it is the only possibility.

Every person, firm and institution in these sentences is invented. Nothing is reproduced from any College Board publication, released test, practice test, question bank or scoring guideline. Note that the real test prints four versions of each sentence and asks which is correct; that format cannot be reproduced here, because four sentences differing only by a comma are treated as one repeated answer by this system's automatic checks, so these questions name the fault and the repair in words instead.

Zestly is an independent study tool. It is not affiliated with the College Board, which owns the SAT, and it is not an exam center.

• Punctuate a series of three or more items, including the comma before the closing conjunction
• Use semicolons between items that contain commas of their own, and say what goes wrong without them
• Tell a plural noun from a possessive one and place the apostrophe accordingly
• Choose between its and it's by expanding the word into "it is" and listening
• Test two adjectives for coordination by reversing them and by joining them with and
• Recognize a colon correctly introducing a single word after a complete clause
• Recognize a dash correctly introducing a summary, without treating an alternative mark as required
• Refuse a comma before a subordinating conjunction that follows its main clause
• Place a period inside a closing quotation mark by American convention, and know what the other convention is
• Decide that a sentence is correct as written rather than hunting for an error that is not there

"The committee heard proposals from firms in Marlow, Ohio, Kenton, Vermont, and Ashby, Oregon." Which choice best describes the punctuation in the writer's sentence?