2. You mustn't/don't have to open the door for a stranger.
3. A stranger may/should trick you.
4. You mustn't/may tell anyone that you are at home alone.
5. You must/might be sure you know your parents' phone number.
6. It must/have to be useful to know people around you.
You have to be over 10 years old to stay at home alone.
You mustn't open the the door for a stranger.
A stranger may trick you.
You mustn't tell anyone that you're home alone.
You must be sure you know your parents phone number.
It must to be useful to know people around you.