The output Signal-to-Noise Ratio of the VHF receiver is defined

The output Signal-to-Noise Ratio of the VHF receiver is defined as（S+N）/N，S means（ ）.

A.A、signal power of an input frequency

B.B、signal power of the output audio

C.C、interference power

D.D、signal power of the output frequency

正确答案是B