单项选择题
With the help of modern technology, ships are able to receive automated broadcast of safety messages（）.
A.by day or at night B.almost round the clock C.somewhat and sometime D.from sunrise to sunset
单项选择题 When the power of a SART is on , it will（）.
单项选择题 The SART should provide a（）indication of its correct operation and should also inform survivors when it is interrogated by radar.
单项选择题 The ARQ mode should be applied（）.
