单项选择题
A.chain locker
B.fairlead
C.anchor
D.contact point of chain with seabed
单项选择题 By regulation，life preservers aboard an uninspected towing vessel must be（）.
单项选择题 As you hold a piece of manila line vertically in front of you，the strands run from the lower left to the upper right. Which type of line is this?（）
单项选择题 An oxygen indicator can be used to determine if there is（）.