You can change your job, you can move house, but friendship is meant to be ________ life.[ ]

A. of  

B. on  

C. to  

D. for

要稳定输出电流，增大电路输入电阻应选用（）负反馈。

A、电压并联

B、电压串联

C、电流串联

D、电流并联