单项选择题
A wind has caused a difference between drafts starboard and port. This difference is（）.
A.list B.heel C.trim D.flotation
单项选择题 Aboard a survival craft,ether can be used to（）.
单项选择题 Above-normal tides near the center of a hurricane maybe caused by the（）.
单项选择题 According to the customs of this port, the work of opening and closing hatch covers is done by（）.
