Answer:
A.
Explanation:
To find out if a call of an animal is missing.
It would be A. because the selection said, "The more scientist's listen to these kind of recordings, the more they notice when expected call are missing".
She may have refused because she either was not in the mood to sleep at the time it was, the bed was uncomfortable, or she was feeling a certain emotion (anger, sadness, etc), etc. You haven’t really provided a source this text was from so this is my guess of what the issue may be.