重点讲解：
1. a couple of 两个；几个；
例句：He gave a couple of loud rings on the doorbell.
他使劲地按了几下门铃zj65Q_sSyXrX.。
2. get used to sth./doing sth. 开始习惯于；
例句：I've got used to being a vegetarian.
我已经习惯吃素食46]U1[F0]j5。
3. fall off 脱落，掉落；
例句：To my great amusement his false beard fell off.
使我感到极其好笑的是他的假胡子掉下来了UzmdZ0G#6OHY#q)L~。
4. keep on 重复；继续；
例句：She kept on working although she was tired.
她虽疲劳但仍继续工作|HQ*^3Y,RM5Z,.w+。