1. It is advised by health experts that windows should be opened now and then for air to _____, which makes the air in your room fresher.
A. go though B. get through C. circulate D. spread around
2. --What do you think of bacteria, _____good or bad?
--_____ to say, but one thing is certain: without bacteria, the world would be quite different from what it is.
A. Are they; hard B. Is it; hardly C. Is it; hard D. Are they; hardly
