Условие задания:

1 Б.
Read these sentences and choose mustn’t, must or needn’t. Write only one modal verb in each sentence. 
  
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1. The room is not dirty. You _____ clean it.
 
   
 
2. They ____ park here. It is forbidden.
 
   
Источники:
www.telegraph.co.uk
Raymond Murphy. English grammar in use- Cambridge: CUP, 379p.