Which is not a functional requirement of GMDSS MF/HF equipment?

Which is not a functional requirement of GMDSS MF/HF equipment?

A.Transmitting.receiving and watch keeping by DSC on 2187.5 KHz.

B.Radiotelephony on 2152 KHz.

C.Transmitting and receiving by NBDP with MF.

D.DSC.NBDP and radiotelephony by HF

正确答案是B