单项选择题
A deadhead is a(n)（）.
A.tree or log awash in a nearly vertical position B.crew member who refuses to work C.upstream end of a land wall D.buoy that is adrift
单项选择题 A barometer showing falling pressure indicates the approach of a（）.
单项选择题 （）the canal transit，the radar was operating.
单项选择题 （）should be used during the poor visibility if the radar’s screen shows heavy sea returns.
