流入电路中一个节点的电流和等于流出节点的电流和。（）
参考答案：对
2，6，12，20，30，( )。
A．38
B．42
C．48
D．56
用所给单词的适当形式填空
1. My purse was stolen on the bus yesterday. ________ (Fortunate), there was no money in it.
2. Mobile phones are _________ (wide) used in most of the cities in China.
3. He put on his coat and went out ________ (quick).
4. She is ______ (good) than Li Ping at swimming.
5. A lot of Chinese people are _______ (pride) of Yao Ming, a famous basketball star in NBA.
6. To our surprise, he suddenly returned on a cold ______ (snow) night.
7. Allie asked me ______ (polite) to put the things away.
8. It’s snowing hard. You must drive ________ (careful).
9. The earth we live on is _______ (big) than the moon.
10. Hainan is a very large island. It’s the second ________ (large) island in China.
, a famous basketball star in NBA.
(careful).