Question 83·Medium·Boundaries
The Pacific Crest Trail—spanning more than 2,600 miles from Mexico to _____ attracts hikers seeking solitude and spectacular mountain scenery.
Which choice completes the text so that it conforms to the conventions of Standard English?
For punctuation-boundary questions, first find the core sentence by temporarily removing any interrupting phrase. Then notice how that interruption is introduced—by a comma, dash, or something else—and remember that such phrases must be set off with matching punctuation on both sides. Quickly eliminate options that mix different marks (like a dash and a comma) or that use colons/semicolons where there isn’t a complete sentence on both sides.
Hints
Check what punctuation is already in the sentence
Look at the punctuation mark that appears immediately after "The Pacific Crest Trail". How does that affect the rest of the sentence?
Identify the extra information
Try reading the sentence without the words between the first punctuation mark after "Trail" and the word "attracts." What is the main sentence, and what part is just extra description?
Think about paired punctuation
When you insert an interrupting phrase in the middle of a sentence, you usually use matching marks on both sides (like two commas, two dashes, or parentheses). Given that, what should come after "Canada"?
Step-by-step Explanation
Find the main sentence and the extra detail
Read the sentence and separate the core statement from the added description:
- Core sentence if you strip out the middle: "The Pacific Crest Trail attracts hikers seeking solitude and spectacular mountain scenery."
- The extra descriptive phrase in the middle is: "spanning more than 2,600 miles from Mexico to _____".
This extra phrase interrupts the core sentence.
Notice how the interruption starts
Look closely at the punctuation right after "The Pacific Crest Trail":
- The sentence reads: "The Pacific Crest Trail—spanning more than 2,600 miles from Mexico to _____ attracts ..."
- That dash after "Trail" signals the start of an interrupting phrase.
In standard English, when an interrupting phrase is set off by dashes, you need two dashes: one to open the interruption and one to close it.
Decide what punctuation is needed after "Canada"
The extra phrase is everything from the first dash up to the end of the distance description: "spanning more than 2,600 miles from Mexico to Canada".
Right after that phrase, we return to the main clause with "attracts hikers...", so we must close the interrupting phrase with the same kind of punctuation mark used to open it.
That means the blank after "Canada" needs a punctuation mark that matches the dash after "Trail".
Test each choice and select the one that matches the structure
Check each option:
- With a comma: "Trail—spanning ... to Canada, attracts ..." → mixes a dash on one side and a comma on the other, which is not standard.
- With a colon: "... to Canada: attracts ..." → a colon must follow a complete sentence, but "spanning more than 2,600 miles from Mexico to Canada" is not a complete sentence.
- With no punctuation: the dash that started the interruption after "Trail" would never be closed.
Only "Canada—" correctly closes the interrupting phrase with a matching dash, so that is the correct answer.