It is only with the help of scientific research _____ bring PM1 air pollution under control.
I’ve just seen no more than one copy of“ Gone with the Wind”in the bookshop opposite. Tom, go and buy ________ back.
They boy said ________ couldn’t he work out the problem but his teacher didn’t know how to do it.
— Why weren't you at the meeting? — I ________ for a long distance call from my sister in America.
We have done things we ought not to have done and ________ undone things we ought to have done.
The two ladies are ________ the same age, but there seems to be ten years ________ them.