Rewrite the sentences using modal verbs of obligation, prohibition or advice.

1 It is not obligatory for students to go to school on Sunday.
2 Our students are not allowed to use their mobiles at school.
3 It isn’t a good idea to take your gloves off when it’s 15 degrees below zero.
4 It isn’t necessary for Jack to wake up early.
5 It is essential for Greg to speak three foreign languages at work.