A)

Don't park your car on bends. It is illegal.

You mustn't park your car on bends. It is illegal.

Perhaps she will agree with it. Who knows?

She may/can agree with it.

Our teacher asked us to tidy the classroom.

We have to tidy the classroom.

I need your help. It's too much work for me.

You must help me.

Look at that balloon. It's over there.

Can you see that balloon?

Don't worry about dinner. I'll make it.

You needn't/don't have to worry about dinner. I'll make it.

It is not necessary to be there.

We don't have to be there.

Why don't you stay with us? No problem!

You can stay with us.

B)

1. It is a very good film. - h. I must buy a ticket.

2. He is not sure now. -  i. He may come tomorrow.

3. She is so different. - f You can't be her sister.

4. It is the last train. - d We mustn't miss it.  

5. It's Sunday today. - b. You don't have to get up early.

6. This exhibition is not free of charge. - g I have to buy a ticket.

7. I'll prepare breakfast myself. -  a. You needn't get up early.

8. The coach leaves tonight and it takes twelve hours to get here. - j. He must come tomorrow.

9. Your address is the same. - e. You can be her sister.

10. We have plenty of time. - c. We can't miss it.