宽带放大器的作用是什么?
参考答案:
对所有频道的信号同时放大,使其具有足够高的电平输入干线。
补全对话
根据语境,用恰当的语言完成对话。
A: Excuse me.小题1:___________________? I haven’t seen him for weeks.
B: Jim’s gone to England.
A: Really?小题2:_________________?
B: He went there last week.
A:小题3:___________________?
B: Yes, He had lived there for 15 years before he came to China.
A:小题4:___________________?
B: He traveled with his friends.
A:小题5:____________________?
B: He’ll be away for about two weeks.
A: Oh, thank you. I’ll phone him this evering.
下列几种估测中,最符合实际情况的是 ( )
A.小明午餐大约吃3 kg米饭
B.一支铅笔的长度大约是1.2 m
C.亳州市四月份的平均气温约为50 ℃
D.电饭锅的功率大约是1000 W