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

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

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

单项选择题Are there many（）and warehouses in the port?

A.wharf
B.wharves
C.wharve
D.wharfs

单项选择题The quartermasters（）steer the ship and help the officer keep lookout.

A.duty
B.on duty
C.at duty
D.in duty

单项选择题The captain is in（）command of the ship.

A.overall
B.over
C.all
D.task

单项选择题The officer of the watch（）a good lookout on the bridge.

A.keep
B.keeping
C.keeps
D.is keeping