A punctuation question with a descriptive phrase tests whether you can separate extra information from the main sentence. Find the subject and its main verb, then ask which words between them add a description. Cross out the extra information to check that the sentence still works. In the middle of a sentence, match the opening and closing marks: use two commas, two dashes, or parentheses. A pause alone doesn't tell you which mark belongs.
Hints
- Hint 1
Look at the verb right after the blank. What noun goes with produces?
- Hint 2
Try removing the description inside the blank. Does what's left still make a complete sentence?
- Hint 3
Find the end of the description. Where does the main sentence continue?
Step-by-step
Cross out and match
Step 1Separate the opening phrase
The words produces eerie, wavering tones tell us what the theremin does, so we're checking the description between the instrument and its verb. Does the comma near the start already open that description? No: it closes Invented in the early 1900s, which tells us when the instrument was invented. That comma belongs to the opening phrase, not to the description inside the blank.
- Step 2
Cross out the description
What happens if we remove an electronic instrument played without physical contact? We still have a complete sentence: the theremin produces eerie, wavering tones that have become synonymous with classic science-fiction soundtracks. The removed words explain what kind of instrument the theremin is and how it's played, but the subject still has its verb without them. The description is extra information that can be removed from the sentence.
- Step 3
Match both ends
How do we separate that description from the main sentence? The opening and closing marks must match, so the dash followed by a comma and the comma followed by a dash are both mixed pairs. The version with only an opening dash leaves the description without a closing mark when the sentence continues at produces. The version with a comma after theremin and another after contact gives the description a matching pair and lets the main sentence continue. Choice C.