Surfing first started on the islands of Hawaii, didn’t it?–Yes, but now it ______ by people all over the world.

He may have seen the film when it was shown last week, _____ he?

More and more people found _________ necessary to have a balanced diet.

Mr. Tiger is always cheerful, and he is always friendly to his students.

Do you know when Dr Smith_____for dinner this evening?—-No,but I think he _____when he is free.