Nature reserves are very important for preserving many animals and plants, which would _______ run the risk of becoming extinct.

After the heavy snow, many students helped to clear away the snow ______ in our school.

 —Shall I turn the heating on?—Sure, it's so cold in here. I'm          freezing.

After two years' research，we now have a ________ better understanding of the disease.(2013·全国Ⅱ)

I hate interruptions, _____when I ’m concentrating on my study.