A punctuation question with extra information tests whether you can find where a side detail starts and ends. Look around the blank for a mark that may open or close that detail, then cross out the extra words to check whether the sentence still works. Does the sentence still say who or what it's about and what they do? In the middle of a sentence, extra information needs matching marks at both ends: two commas, two dashes, or a pair of parentheses.
Hints
- Hint 1
Look back from the blank for the start of a side detail. What mark introduces the words beginning with spanning?
- Hint 2
Try crossing out the detail about the trail's length and route. Does the remaining sentence still have a subject and a main verb?
Step-by-step
Find the insert and match its marks
Step 1Find what the dash opens
The dash in The Pacific Crest Trail—spanning sits after the trail's name. What does it introduce? The words beginning with spanning describe the trail's length and route, and that description continues through the country name at the blank. This could be an insert, a piece of extra information the sentence can do without. To settle the punctuation, find where the main sentence picks up again.
- Step 2
Cross out the description
Which word gives the trail its main verb, the word that says what it does? In attracts hikers seeking solitude and spectacular mountain scenery, attracts does that job, while spanning only describes the trail. Let's cross out the description and its opening dash: the trail's name now leads directly into attracts, leaving a complete sentence about the trail drawing hikers. Since removing that whole detail leaves a complete sentence, the insert ends right before attracts.
- Step 3
Close with the matching mark
An insert in the middle of a sentence needs the same kind of mark at both ends. The dash in Trail—spanning is the opener, so we need a dash at the blank. The version with a comma would mix marks, while the versions with a colon or no punctuation wouldn't close the insert. Canada— adds the closing dash that lets the sentence continue to its main verb. Choice B.