一、

1．needn't

2．must

3．can't

4．do

5．Need, must

6．Would

7．have to

8．May / Can; may /can

9．Shall

二、

1．have to

2．is able to

3．must

4．was, able

5．ought to

三、

1．C         2．C         3．B          4．D         5．D