— Betty ______ john and is our headmaster now.    

— Really? In my opinion, she herself should be ______ by someone else, too.[ ]

A. has taken place of; replaced              

B. has placed; taken place

C. has taken the place of; replaced          

D. taken place of; replace

调节器的比例度越大，则放大倍数（），比例调节作用（）。

A.越小

B.越大

C.不变

D.越弱