After ____ seemed like hours he came out with a bitter smile.

It is the prevention of disease ______ its successful treatment that has led to the rapid increaseof the world’s population.[ ]

－I think students should be allowed _____ homework with friends.－I disagree. They talk instead of ________ homework.

British people say “please” and “thank you” all the time ______some people in Asia may think it unnecessary.

I’d rather ride a bike as bike riding has _____ of thetrouble of taking buses.