You’d better _______ too much meat. You are much too fat.
The students are doing some cleaning. Some are sweeping the floor, ________ are cleaning the desks and chairs.
If he _________ here next week, I ____there.
I don’t know _______ .
----I feel tired and sleepy. -----Why not stop _______ ?
If there are ______ trees, the air in our city will be _______ cleaner.