单项选择题
A.by day or at night B.almost round the clock C.somewhat and sometime D.from sunrise and sunset
A radio determination system based on the comparison of...
单项选择题A radio determination system based on the comparison of reference signals with radio signals reflected,or retransmitted from the position to be determined,is（）.
A.DF B.Radar System C.DSC System D.COSPAS-SARSAT
What information will a distress alert contain?（）A.natu...
单项选择题What information will a distress alert contain?（）
A.nature of distress B.type of assistance required C.course and speed and time at which the information was recorded D.A, B, C are all right
The ARQ mode should be applied（）.A.when two stations co...
单项选择题The ARQ mode should be applied（）.
A.when two stations communicate with each other B.in any radio system and at any time C.when one ship sends a message to another station D.for communication among some stations
