单项选择题
RESULT OF SEARCH NEGATIVE means（）.
A.the search has found nothing B.the derelict has been found C.the derelict has been located D.the derelict has been sighted
单项选择题 One of the signals，other than a distress signal，that can be used by a vessel to attract attention is a(n)（）.
单项选择题 Generally，you can best keep a vessel under steering control when the vessel has（）.
单项选择题 Generally speaking，the most favorable bottom for anchoring is（）.
