Once upon a time, there was a gray cat. The cat liked to play with a ball. One day, the ball went near a big bin.
The cat went to the bin to get the ball. But the ball did vanish! The cat was very sad. It looked and looked, but could not find the ball.
The cat should have been careful near the bin. The cat learned that if it was not careful, things could go away. The cat was sad, but it knew to be more careful next time.
