The telephone _____ three times in the last hour, and each time it _____ for my sister.
___ is a good idea to keep quiet about the problem.
You’d better find an English pen friend ___ improve your writing.
There are 2100 students __ all in our school.
You’d better __ electricity; it would be dangerous.
Mum, I think I’m __ to get back to school.---Not really, my dear.You’d better stay at home for another day or two.