The ELT, an electronic, battery-operated transmitter, sends forth a distinctive _______ on 121.5 MHz.
A.audio tone
B.Mayday call
C.alarm
D.either A or B
正确答案是A
The ELT, an electronic, battery-operated transmitter, sends forth a distinctive _______ on 121.5 MHz.
A.audio tone
B.Mayday call
C.alarm
D.either A or B
正确答案是A