he years, people have learned from ants that teamwork and perseverance are indeed two key ______ to success.

Try ________ she might, Sue couldn’t get the door open.(2011·全国Ⅰ)

The enthusiastic physician takes part in all community services. ________, he often provides his medical service to the neighborhood.

Now that the sign reads, “No person ______ smoke here”, please choose a seat in the smoking area over there if you _______ smoke.

I’ll go to bed as soon as my homework______