People cut down too many trees, _____ the greenhouse effect becomes more and more serious.
—___________ you like the TV program Dad, Where Are We Going?—Yes. But I like Super Brain better.
I’m as tall as my cousin although he’s _________ than me.
—Would you like ________ Emily and Carol?—Of course. I hear they are twins and play the piano well.
Be quiet, boys and girls! It’s time for class. __________ Unit 3 in your books.
Mr. Cooper is _________ tired __________ do anything this morning.