全向天线为了保证通信质量,采用空间分集的方式。收发共用天线与收天线之间的水平距离()米,并且必须()否则空间分集就失去意义。
参考答案:应大于5;处于同一水平面上
根据句意和提示完成句子。
1.—How long have you studied English?
—For ______ (将近) six years.
2. It's easier to learn a foreign ______(语言) when you visit the country.
3. I've lived in Beijing______ (自从) 2001.
4. They are very______ (与……不同) from our school.
5. That______ (听起来) very surprising.
6.—Do you like______ (宠物)?
—Yes, very much.I've had a lovely dog for 5 years.
7. You're very ______ (幸运) to have a chance to go abroad.
8.—I don't feel very well today.
—Well, are you______ (生病)?
下列化合物中()是碱
A、氯化钾
B、氢氧化钾
C、硫酸
D、氟利昂