Question

Which sentence demonstrates an error in parallel structure?
A.
Smoke oozed from the volcano's peak, the ground vibrated, and, with a thundering roar, a cloud of fire shot into the air.
B.
The Web site needs to be changed to describe what time the game begins, how to get to the stadium, and, to prevent unnecessary citations, where to park legally.
C.
At my last appointment, my dentist talked to me about removing my wisdom teeth, filling my cavity, and, less importantly, how to whiten my smile.
D.
After driving around the city, I learned that the library is on Heartz Street, the post office is on Bethel Road, and, conveniently, the city pool/recreation center is on Parkway Boulevard.
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Answer 1

C

Explanation: The list mixes gerund phrases ("removing my wisdom teeth," "filling my cavity") with an infinitive/wh‑question clause ("how to whiten my smile"), so the items aren't parallel.

Revision options:
- Make all gerunds: "…about removing my wisdom teeth, filling my cavity, and whitening my smile."
- Make all "how to" clauses: "…about how to remove my wisdom teeth, how to fill my cavity, and how to whiten my smile."