单项选择题
A number of bags are worn-out（）a certain extent.
A.at B.in C.on D.to
单项选择题 Allowance for fresh water refers to（）.
单项选择题 A vertical shift of weight to a position above the vessel’s center of gravity will（）.
单项选择题 Although KG for a vessel in lightweight is relatively high，the vessel is stiff because（）.
