A punctuation question with a side detail tests whether you can see where that detail starts and ends. Find the subject and ask which verb tells what it does. Then cross out the side detail to check that a complete sentence remains. Extra information in the middle needs matching marks at both ends: two commas, two dashes, or parentheses. A verb inside the side detail can make the sentence seem complete even when its main verb hasn't arrived.
Hints
- Hint 1
Look at the words beginning with which. Find where that detail stops, and ask which verb carries on the sentence about the book.
- Hint 2
Try removing the detail that begins with which. Check where the remaining sentence picks up again, then look at the punctuation where the removed words started.
Step-by-step
Find the extra detail and match its marks
Step 1Find the extra detail
Start with Rachel Carson’s groundbreaking book, the thing the sentence is about. Why does the comma after the title lead into which warned of the dangers of pesticide? Those words tell us more about the book, so the comma opens an extra detail the sentence can do without. The punctuation at the blank needs to show where that detail ends and the main sentence continues.
- Step 2
Find the book's own verb
Which verb carries on the main sentence? In which warned, warned belongs to which, so it's part of the extra detail rather than the book's main verb. The main sentence continues with helped spark the modern environmental movement, which tells us what the book did. Cross out the warning detail, and we're left with the book and its title followed directly by helped spark. Because that sentence still works, the extra detail ends right before helped.
- Step 3
Match the opening comma
An extra detail in the middle needs matching marks, so the comma after the title needs a closing comma. Why not add and as well? That word would join helped spark to warned inside the detail, leaving the book without its own main verb. The choice use, closes the extra detail before helped spark and lets the main sentence continue without a linking word. Choice D.