Answer:
B. Nick
Step-by-step explanation:
Nick offers this reflection on the first page of the novel, and his words have an important foreshadowing function. The entire story that Nick is about to relate arises from his having become a confidante for two opposing men, Tom Buchanan and Jay Gatsby. The antagonism between these men has disastrous effects, and Nick finds himself caught in the middle of it. This experience explains why, as he observes in the second sentence quoted here, Nick now goes to any lengths necessary to avoid the confidences of others.