单项选择题
A life preserver or buoyant work vest is required to be worn on a ship when a person is （）.
A.working on the rig floor B.working over water C.working on the pipe racks D.operating line throwing equipment
单项选择题 A latitude line will be obtained by observing a body （）.
单项选择题 A lashing used to secure two barges side by side，lashed in an "X" fashion，is called a （）.
