Ответ:

5. 1 )She must not - she mustn't

2) They can not - they can't

3) You need not - you needn't

3) I do not have to - I don't have to

6. 1) You don’t have to wash the dishes, my sister is already doing them.

2) Hey, pal, eating in the library isn’t allowed.

3) I can’t give it to you, I need it to watch a CD my teacher sent me!

4) Hey, can you please be quiet? You are disturbing other people.

5) Please pay the rent on time, because we too, need the money, if you don’t pay it in time, we will kick you out.

(к вопросу 6. взяты ответы от пользователя pogvov20)