1) You mustn't take photos in the museum.

2) You must cross the street at the zebra crossing.

3) You mustn't park here.

4) You must wear a helmet on a motorbike.

5) You mustn't talk in the library.

6) You must put your letter in the bin.

7) You mustn't take your dog with you to a restaurant.

8) You must look after your pet.

Ответ:

1) You mustn't take photos in the museum.

2) You must cross the street at the zebra crossing.

3) You mustn't park here.

4) You must wear a helmet on a motorbike.

5) You mustn't talk in the library.

6) You must put your letter in the bin.

7) You mustn't take your dog with you to a restaurant.

8) You must look after your pet.

Там было подсказка, это + и - !!!

Если - тогда mustn't

Если + тогда must