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: Bob opened the curtains. There were birds in the yard. They were eating his garden plants. He ran outside yelling. The birds flew away.
 selected sentence: Bob opened the curtains.

Bob possesses curtains >Causes/Enables> Bob opened the curtains