The billiards are bulging

One day, Xiao Ming was about to play table tennis.

The two of them were playing, and Xiaohong suddenly found that the billiards were flat. What can I do? At this time, Dad walked over and said: "You can put the billiard ball in the hot water for a few minutes."

So Xiaohong and Xiao Ming ran home. They asked their mother to help me with a hot water. Xiaohong put the billiard ball in the basin, and after a while the billiards bulged.

Xiaohong and Xiaoming smiled happily.

The first grade of Kangleli National Primary School in Xicheng District, Beijing: Li Wei