为什么要钻定向井？
参考答案：
地面环境条件的限制；地下地质条件的要求；处理井下事故的要求。
用所给动词的适当形式填空
1. Mozart __________(make) a lot of famous music.
2. His father __________(die) for five years.
3. There are many __________(music) playing the piano.
4. He __________(teach) us English well, doesn't he?
5. Please ask him __________(not watch) TV before he finishes his homework.
6. It's best __________(read) English in the morning.
7. If it __________(rain), my father __________(take) me to school in his car.
搜救雷达应答器（SART）工作频率的范围应为是多少？（）
A、1-27.5MHZ
B、406-406.1MHZ
C、1530-1544MHZ
D、9200-9500MHZ
