讲解文本：

grind one's teeth 磨牙

grind 磨，碾

Some people grind their teeth while they are asleep.

有些人睡觉时磨牙齿。

My roommate Jack always grinds his teeth in his sleep, which is a totally disaster.

我室友Jack喜欢睡觉磨牙，这对我就是个灾难。

疯狂练习吧!