重点讲解：
1. knock on
敲；击；
eg. She went directly to Simon's apartment and knocked on the door.
她直奔西蒙的房间，敲了敲门。
eg. Please do not enter before knocking on the door.
进来前请先敲门。
2. on the road
在旅途中；在路上；
eg. He hoped to get a new truck and go back on the road.
他希望能有一辆新的卡车，重新上路。
eg. There are more cars on the road in the summer than in the winter.
夏天路上的车子比冬天多。
3. sleep tight
好好睡；睡得香；
eg. Since that night, all the residents around could not sleep tight.
从那个晚上开始，附近的居民都不得安眠。
eg. I'm not a little tired evening. So sleep tight.
我昨晚很累,因而睡得很香。
eg. Nightie-Night, sleep tight, have a sweet dream.
晚安，睡好了，祝你做个甜蜜的梦。