单项选择题
A.a heavy anchor with an extra long line used to anchor in deep water
B.a cone shaped bag used to slow down the wind drift effect
C.a pad eye to which the sea painter is made fast
D.made of wood if it is of an approved type
单项选择题 A mercurial barometer at sea is subject to rapid variations in height (“pumping”) due to the pitch and roll of the vessel. To avoid this error，measurements of atmospheric pressure at sea are usually measured with a(n)（）.
单项选择题 A heavy steel device that is set on the sea floor and used as a drilling template in offshore drilling operations is called a（）.