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: Nicole loved to write by an oil lamp at night. But it was messy to change the oil and the wick. When she had to do so, it was a challenge. She'd bring rags to protect the table. But when everything was ready, she could enjoy a nice light.
 selected sentence: When she had to do so, it was a challenge.

Nicole changes the oil and the wick >Causes/Enables> It is a challenge