如图所示，A为信号源，B为接收器，A、B之间有一真空区域．当信号源A分别发射出次声波、紫外线、可见光和无线电波信号时，接收器B不能接收到的信号是(     )

A．次声波　　　　　

B．紫外线

C．可见光

D．无线电波

I have worked with children before, so I know what ______ in my new job.

A．to expecting

B．expected

C．to expect

D．being expected