简介：
【自主归纳】be supposed to do...
1. Everyone is supposed to wear a seat-belt in the car. 每个人在汽车里都应该系安全带。
2.The new laws are supposed to prevent crime. 这些新法令本应该起到防止犯罪的作用。
3. be supposed to后面接“have + 过去分词”时，表示“本应该做某事而没做”。
You are supposed to have handed in your homework by now.现在你应该已经把作业...