The fisherman is hesitant toward the end of the story because

B.) he knows the fish will be upset by his latest request

Explanation:

The question is related to the story about "The Tale of the Fisherman and the Fish," which was written by Alexander Pushkin. This is a fairy tale which centers on the life of a poor old man and a woman. Upon fishing, the old man found a "golden fish." The fish asked him to spare his life and in return he was given a wish. The old man didn't want anything, however, when he told his wife about it, his wife wanted him to ask the fish for a "new trough." This was followed by many other wishes.

In the end, she wanted to become the "Ruler of the Sea." This made the fisherman hesitant because he knows that the golden fish would be upset by his latest request. His wife wanted more wishes from the fish, thus she wanted to control it. The fish then stopped the greed of the wife by putting her back to her usual situation.

So, this explains the answer.