One of the main differences between the way an American talks and the way the rest of the world talks is that they don't really move their lips『嘴唇』. They create most of their sounds in the throat『喉部』, using their tongue『舌头』very actively. If you hold your fingers over your lips or clench your jaws『握住喉部』when you practice American English, you will find yourself much closer to native-sounding speech than if you try to pronounce every single sound very carefully.

　　[BRIAN小结]

　　1、Americans don't really move their tips when they talk. /美国人在说话的时候嘴唇并不动。

　　2、clench:握紧；咬紧

　　经典例句：The mom told her son to clench her clothes. /母亲叫她的儿子紧抓住她的衣服。