限幅放大器是利用二极管的正向特性，将信号限幅在（）mV以下。
A.400
B.500
C.600
D.700
参考答案：D
重庆奉节小寨天坑是世界迄今发现的最大天坑，被誉为“天下第一坑”，它属于地下岩溶地貌景观。
He has been fired and will have to _______ charge of his office tomorrow.
A．take over
B．hand over
C．get over
D．go over
