A punctuation question near the end of a long sentence tests how the final words connect. Read both sides of the blank and check whether each side can stand alone. To do that, find who or what each verb belongs to, including verbs in parts that describe a noun. Periods and semicolons separate complete sentences; a comma attaches extra information to a complete sentence; use no mark between words that belong together. A phrase can contain a verb without being a complete sentence.
Hints
- Hint 1
Read from “the results revealed that” through the blank. Find who or what each verb belongs to so you can test whether that thought is complete.
- Hint 2
Check what the final verb belongs to. Does could inform finish the whole phrase, or is it inside the words beginning with that?
- Hint 3
Try the cross-out test. Remove the words beginning with “a discovery” and ask whether the sentence still works.
Step-by-step
Test what can stand alone
Step 1Finish the thought before the blank
Read from the results revealed that through the blank: the results revealed that microstructures reduce turbulence. Could that thought stand alone? Yes, because results is the subject, the thing we're talking about, and revealed is its main verb, which says what it did. The words beginning with that finish what was revealed, so the thought before the blank is complete.
- Step 2
Find what the final verb belongs to
Can a discovery that could inform the design of quieter aircraft stand alone? The verb could inform belongs to that in the words describing the discovery. The phrase a discovery has no main verb of its own, so it's a fragment, a group of words that can't stand alone. The versions turbulence; and turbulence. would cut off those words as if they formed a full sentence.
- Step 3
Test for extra information
What does a discovery refer to? It names the finding that the wing microstructures reduce turbulence. Cross out the words from a discovery to the end, and the sentence still works, which makes those words extra information about the finding. The version turbulence leaves that extra information unmarked, running the completed finding into the comment about it.
- Step 4
Attach the phrase at the sentence's end
Extra information at the end of a complete sentence needs one comma before it, with the period marking its end. The version turbulence, places that comma before a discovery. Choice D.