Key to "Modals" exercises

Here's the key to the exercise on Modals:

1-      Oh, she’s so rich; she needn’t/doesn’t have to work.

2-      You shouldn’t hit your baby brother. That’s horrible behaviour!

3-      You needn’t/don’t have to book a hotel room. November isn’t a busy month.

4-      I should have seen a doctor earlier; my illness has worsened.

5-      Look at that sign; we mustn’t/can’t walk on the grass.

6-      The cinema is crowded; the film must be good.

7-      You needn’t/don’t have to look up every word you don’t understand.

8-      We shouldn’t have told her about the accident; she broke down.

9-      Ali isn’t at home; he must have gone out.

10-  I haven’t decided yet but I may/can/might/could travel to Tangiers next holiday.

11-  I can’t read; it’s too dark.

12-  You must/have to take off your shoes before you enter the mosque.

13-  They could have won the match if the referee had been fair.

14-  You can/may watch TV after you do your homework.

15-  All his clothes are wet; he must have walked under the rain.

16-  Hassan has caught the flu. He shouldn’t have taken a cold shower.

17-  My sight is decreasing, I should change my glasses.

Well, yes, you should have changed them a long time ago.

18-  You needn’t/don’t have to continue the treatment, you have recovered now.