In a weather report “GMT” stands for（）.

单项选择题It is danger for vessels without the use of（）to approach the estuary in such poor visibility.

A.Loran C
B.Direction Finder
C.Gyro- compass
D.Radar

单项选择题When visibility is 20 nautical miles, we say that visibility is（）.

A.very good
B.good
C.poor
D.moderate

单项选择题Our ship has not been to shipyard for a long time, the fouling on the ship’s hull greatly decreases her（）.

A.resistance
B.weight
C.speed
D.displacement

单项选择题Radar is not only to obtain（）,but also to measure their distance away from you.

A.brightness of obtain
B.color of targets
C.shape of targets
D.bearing of objects

单项选择题The anchor was then（）and the siren sounded.

A.aweigh
B.weight
C.weigh
D.weighing