- Look! It’s raining again.  -- Why _________it rain on Sundays? We are always staying inside! What a nuisance!.

 You_______ play with fire, Tom. It's dangerous.

It has been announced that students _______ remain in their seats until all the papers have been collected.

－Is that Mary?－No, it _______be her. She has gone to Tokyo. 

— __________ we leave the library before 5 o’clock?— No, you needn’t. You can stay here until 5:30.