传统理论认为，汇率下降，则（）。
A.本币升值
B.本币贬值
C.不利于出口而利于进口
D.不利于进口而利于出口
参考答案：A, C
—We'll go to the party to be held in Qinghai Grand Theater at 8 tonight. Could you join us?
—I'm afraid I can't. I ________ the holiday plan with my friends.
A．am discussing
B．have discussed
C．will be discussing
D．will have discussed
压电式传感器后面的放大器的主要功能为（）。
A、阻抗变换
B、信号放大
C、阻抗变换和信号放大
D、不确定
