求如图所示的交变电流的有效值，其中每个周期的后半周期的图象为半个周期的正弦曲线

A、5A

B、5A

C、A

D、A

-What’s your idea if someone wants to talk to you while you are doing your homework?  

-I may get _       because he is too impolite.      [ ]

A. happy    

B. sad        

C. surprised  

D. annoyed