cho các từ : must,can , should have, had to, needn"t, was able to, don"t have to, should, can"t, mustn"t, needn"t, must, ought, didn"t need to, can"t.
1 it is getting very late. we..... go home now.
1 I couldn"t go out last night because I........babysit for my sister.
3 you...........pay me back the money you owe me until next month.
4 " we ought to be getting ready now. "Yes, I guess we............"
5 we......... touch anything in this room until the police arrive.
6 It....be Helen. She has gone to Hanoi.
7 we need not do the washing up now. We ......do it tomorrow.