8.(28)
A. Why did you do it?
B. What does it do?
C. What can we do?
D. How do you do?
9.(29)
A. I’ll give you a discount.
B. They don’t accept checks.
C. Let’s go check it out.
D. The store is selling at a discount.
10.(30)
A. Who did it?
B. What’s the weather like?
C. What a bad idea!
D. How terrible!
反馈型振荡器的环路增益是反馈信号与激励源信号的比值
A. 对
B. 错