Which of the following is a complete sentence?
A. When the rain, in heavy, sweeping torrents
came rushing across the quivering plain.
B. Ever since I was very young, I have loved the
sport baseball.
C. Although I had known Benjamin ever since
Ms. Granger's Class in the third grade.

B.

Explanation:

a sentence like these must make sense to say out loud. you wouldn't just end off your sentence without explaining it, so whichever sounds most like the one you would say out loud is a complete sentence.

the right ones are in bold.

daintly refers to the fact she was reaching for what she ate, not necessarily what she is like.

greatest charm as in she possessed (=had) the greatest charm.

pleasant (her demeanor)

speaking (of her sensibility)

dead refers to the hypothetical mouse.

bleeding refers to the hypothetical mouse.