1．I really think you should(should/could) visit the Three Gorges Dam. It's fascinating.
2．It will be(will be/can be) a great trip because there are so many interesting things to see.
3．We had to(must/had to) return by the end of February.We started work again in March.
4．People mustn't(can't/mustn't) park here because it's a fire exit.
5．There used to(would/used to) be a temple, but now there are only high buildings.
Ⅱ.用can，could，must，should，have to的正确形式填空
1．I made it clear to them that they must hand in their papers before 10 o'clock in the morning.
2．Since you have got such a good chance, you should make full use of it.
3．He has to/had to work hard to remain ahead of his classmates.
4．Mum told her son to make a rule to leave things where he could find them again.
5．Peter can be really rude at times even though he's a nice person in general.
