The key to exercise solutions in chapter 4c - Grammar in use for the textbook On Screen B2+ - Student's Book with authors Virginia Evans and Jenny Dooley from Express Publishing
Question
Rewrite the sentences using modals.
Answer
You mustn’t / can’t enter the lab.
Paul may be late for the party.
When I was ten, I couldn’t ski.
You should / ought to find a summer job and save money.