Select the subject of the sentence.

At the last minute, the librarians asked Nick Fury to sort all of the books.

The librarians.

The subject of the sentence is "the librarians".

To select the subject of the sentence, we need to identify who or what is performing the action in the sentence. In this sentence, the action being performed is "asked." Who did the action of asking? The answer is "the librarians." Therefore, "the librarians" is the subject of the sentence.