Question

Which of the following sentences is correct?

A. She is the person whom he had found sleeping in the library.
B. The musical group whom won the top prize are from my hometown.
C. That author is the one who I saw at the bookstore today.
D. Against who did you think you would compete in the contest?

Answer 1

a would be the correct answer

Answer 2

Hi.
The answer is A. She is the person whom he had found sleeping in the library.

Why? Because turn it into a question: 'Who did he find sleeping in the library?'
You would say 'He found her'

If you say 'her' or 'him' as an answer to a question, you would use whom.