FV同步检波器需输入（）的副载波。
A.FV和±90°
B.FU和±90°
C.FV和±180°
D.FU和±180°
参考答案：A
I was born ________ 7th October ________ Zhenjiang.
A．on, in
B．in, on
C．on, on
D．at, in
放大电路中的负反馈有哪四种类型？
