A punctuation question with nested details tests how you separate extra details from the main sentence. Read around the blank and check how the parts connect, then test which parts can stand alone. Use the sentence structure: paired commas surround extra details, while a semicolon joins complete sentences. A colon follows a complete sentence and introduces what comes next. No punctuation is needed when words connect without a break, so check whether the sentence needs a break or a mark to close a pair.
Hints
- Hint 1
The sentence uses which twice. Check the punctuation after the second one and ask what words it opens.
- Hint 2
Find what the second which refers to. How does detected connect to it?
- Hint 3
Check where each added detail begins and ends. How would removing each detail affect the sentence?
Step-by-step
Track the inner insert
Step 1Find what the nearby comma opens
The comma in and which, unlike earlier field comes right before a comparison with earlier field surveys. Since the choices change punctuation at the blank, what does that comma open? It opens an insert, a piece of extra information beginning with unlike. This smaller insert sits inside the longer description of the analyses.
- Step 2
Cross out the shorter detail
Where does that smaller insert end? Cross out the words from unlike through the blank, and the second which connects directly to detected traces of basalt. The crossed-out words compare these analyses with earlier field surveys, while the remaining words say that these analyses found basalt. Because which stands for the analyses and detected tells what they did, the comparison ends at the blank, before detected.
- Step 3
Find what the later comma closes
The comma in basalt, do not by themselves establish sits where the main sentence continues. What happens if we cross out the whole description beginning with the first which? We get a complete sentence saying that Mineral analyses don't establish that the depression is volcanic. So the comma after basalt closes the larger description, not the shorter comparison.
- Step 4
Match the inner pair
An insert in the middle of a sentence needs the same kind of mark at both ends. The comma in which, unlike earlier field means the blank needs a closing comma, so use surveys,. Choice A.