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: John's friend visited him. He came with his dog. When John saw the dog constantly scratching itself, he became worried. His friend said the dog might have fleas or it might not. John became worried and told his friend to leave.
 selected sentence: When John saw the dog constantly scratching itself, he became worried.

John's friend visits with his dog >Causes/Enables> The dog constantly scratches itself