Answer:
B. While I was reading quietly, a rainstorm dropped inches of rain on the town.
Step-by-step explanation:
It's not always the case that a dangling modifier is the last word in a statement. A hanging modifier can be as little as a single word if it is not clear what portion of the sentence it is supposed to modify.
"Reading quietly, a rainstorm dropped inches of rain on the town."
This sentence is unclear as who is reading? A rainstorm cannot read making this a dangling modifier error.