Fill in the necessary modal verbs can\ can`t , may\may not , must\mustn`t , to have to in the correct form 1) ..........

1) Can you swim well? - Oh ,no. I can\'t swim very well. 2) Ben, you must be polite with your sister! 3) May I come in? - No, you may not. You are late. 4) Boys, you mustn\'t talk in class. 5) Helen has to work hard, because she wants to pass her exam.