You mustn't/don't have to open the door for a stranger. a stranger may/should trick you. you have to/might answer the phone. you don't have to! may tell everybody that you are home alone . you must/might know your parents' phone number. it must/have to be wise to know your neighbours .
You mustn't open the door for a stranger. A stranger should trick you. You might answer the phone. You don't have to tell everybody that you are home alone . You must know your parents' phone number. It have to be wise to know your neighbours .