A punctuation question with extra information tests whether you can find where a description begins and ends. Read to find the subject, who or what the sentence is about, and its main verb. Cross out the description and check that a complete sentence remains. Extra information in the middle takes matching commas, dashes, or parentheses: the two ends must match. A semicolon instead joins two complete sentences.
Hints
- Hint 1
Read the second sentence all the way to the period. Find the verb that tells what the central structure is made of.
- Hint 2
Look at the words about the bustling markets. If you remove them, does the rest of the sentence still work?
- Hint 3
For each completion, check both ends of the description. How does each version connect the description to the rest of the sentence?
Step-by-step
Find the insert and match its marks
Step 1Find the structure’s main verb
Read past the blank to consists of towering basalt walls, which tells us what the structure is made of. What consists of those walls? The site’s central structure does, so the structure already has its main verb, the verb that says what the subject does or is. That means we need to check whether the words before that verb add extra information or give the structure another main verb.
- Step 2
Test the description and find its end
What do the words ringed by bustling markets add? They tell us that markets surrounded the structure, and removing the whole description leaves a full sentence saying what the structure is made of. So these words form an insert, a piece of extra information the sentence can do without. The word ringed describes something done to the structure; was ringed would make it a main verb, even though the structure already has one. The dash in markets—consists closes the insert where the main sentence continues.
- Step 3
Add the matching opening mark
How should the blank match the dash in markets—consists? Extra information in the middle needs the same mark at both ends, so a dash must open this insert after structure. The choice structure—once adds that opening dash and makes the words about the markets a description rather than a second main verb. Choice C.