We laugh at jokes,but seldomabout how they work.
I met Professor Green in the street____ and he told me he would soon leave for Britain.
--Did you telephone the manager’s office? ---Yes.He ____ back before 9 this morning.
--Do you remember ____ he came? --Yes, I do.He came by car.
He ____ his home for a week.
--What’s ___ population of China? --China has ____ population of 1.5 billion.