Radio check requirement order is _______ .

Radio check requirement order is _______ .

A.1. the station being called, 2.A/C call sign, 3. radio check, 4. frequency

B.1. radio check, 2. frequency, 3. A/C call sign, 4. the station being called

C.1. the station being called, 2. frequency, 3. radio check, 4. A/C call sign

D.1. the A/C call sign, 2. the station being called, 3. radio check, 4. frequency

正确答案是A