单项选择题
A dead reckoning (DR) plot（）.
A.must utilize magnatic courses B.must take set and drift into account C.should be replotted hourly D.should be started each time the vessels position is fixed
单项选择题 A deck fitting, used to secure line or wire rope, consisting of a single body with two protruding horns is called a（）.
单项选择题 A deepwell pump is a type of（）.
单项选择题 A definite advantage of using water as a fire extiguishing agent is its characteristic of（）.
