Definition: In this task, you will be given a short story. One sentence from the story is chosen. Consider the events that happen before that sentence, or are likely to have happened before it. Does any of them directly cause it, or simply make it possible? You should write your answer in the form " A >causes/enables> B". Try to use phrases and sentences from the story to compose your answer when possible.
Input: story: Steve studied all night for an exam the next day. In the morning, he gulped coffee to stay awake for the test. By the time of the test, Steve was tired and jittery. The words on the paper seemed to swim before his eyes. Fifteen minutes into the test period, Steve had fallen asleep.
 selected sentence: Fifteen minutes into the test period, Steve had fallen asleep.

Steve studies all night >Causes/Enables> Steve falls asleep