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: Sam was running for the train. On the way, she tripped over the curb. She fell and scraped bother her knees. She got back up quickly, but did not make the train. She had to wait 30 minutes for the next one.
 selected sentence: She fell and scraped bother her knees.

Sam trips >Causes/Enables> Sam falls