2 Complete the sentences with must or mustn't and the verb in brackets. 1 Children.... (go) to school. 2 You.... (wear) a helmet when you ride a motorbike. 3 You.... (swim) on a beach when the flag is red. 4 You.... (talk) in a library. 6 5 When the traffic lights are red, you .... (stop). You.... (forget) your passport when you travel to another country.​