Which sentence uses the underlined
vocabulary word incorrectly?
A. My brother annoys me when he is sagacious and
starts stuttering all of his words.
B. He squealed in ecstasy when he won the jackpot.
C. With disapprobation on her face, she accepted
my sloppy, handwritten paper.

The answer would be Option A.

Explanation:

This is because the meaning of "sagacious" in Option A means to be wise   and /or good judgement. That is with sharp contrast with the rest of Option A's sentence. This is because good judgement is an antonym with "annoys me." And nobody with good judgement is annoying, at least in a personal stance.

Looking at the other options, Option B would be used correctly as "ecstasy" means happy and/or excited. And this fits into the sentence just fine, because he won a jackpot! Who wouldn't be excited?

Option C would also be used correctly as "disapprobation" means to dislike. And this fits into the sentence, like Option B. This is because the handwriting is "sloppy", meaning that it's most likely rushed and lower quality.

This leaves only Option A, as the only sentence to be used in incorrect context.