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: Carla and Sam spent the morning building a sand castle. They wanted it to be the best one on the beach. They took a break for lunch. When they came back it was gone. The tide had rolled in, smashing it.
 selected sentence: When they came back it was gone.

Carla and Sam leave a sand castle on the beach >Causes/Enables> The sandcastle disappears while Carla and Sam are gone