https://online2.tingclass.net/lesson/shi0529/0009/9907/168.mp3
https://image.tingclass.net/statics/js/2012
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!
