1. — Can you take good care of y _____ while I'm not at home? — Of course, we can.
2. — Does this piece of m _____sound nice?
     — Yes. It's wonderful.
3. We can play tricks (恶作剧) on friends on April 1, but they will not be a _____ with us.
4. India has the second l _____ population in the world.
5. Yesterday the teacher told us the earth r _____ around the sun.
6. I didn't have my breakfast this morning. Now I feel so h _____ that I want to do nothing.
7. The Yellow River, the world's f _____  longest river, has watered some of the oldest farms on Earth.
8. When I told them the funny jokes, they couldn't help l_____ .
9. Some scientists said,"If you often go running alone in the morning, it would become b _____ for your
    brain, you'd better run with your friends."
10.The plane flew higher and higher. At last it d _____ in the sky.
11.Now computers are w _____  used in our office.
12.The Red Army men walked a long way and their shoes were all w _____ out.
13. Li Ming can find many new things that we don't know on the Web, and he'd like to s _____  them
      with all of us.
14.What should you do when you suddenly hear shouts of "fire" and smell smoke t _____ the door?

[     ]

A. Though
B. Because
C. As
D. While