teeth后面跟is还是are

后面用are，例如：

1.The teeth are like razors. Once you get tangled up it will never let you go.其牙齿就像剃刀，一旦咬住你它就绝不会松开。

2.Canine teeth are for piercing and killing prey, and tearing flesh.犬齿用来咬穿、咬死猎物，还可以撕肉。

3.Cavities in teeth are caused by decay.牙齿上的空洞是由龋蚀造成的。