单项选择题

The average height of the surface of the sea for all stages of the tide over a 19 year period is called（）.

A.mean high water
B.mean low water
C.half-tide level
D.mean sea level

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单项选择题

The 3-cm radar as compared to a 10-cm radar with similar specifications will（）.

A.give better range performance in rain，hail，etc
B.display small targets in a mass of dense sea clutter at a greater range
C.have less sea return in choppy rough seas
D.display a more maplike presentation for inshore navigation

单项选择题

The “urgent” priority should be used for messages（）.

A.concerning the Safety of Life at Sea (SOLAS)
B.detailing important navigational warnings
C.containing information concerning the safety of a mobile unit or person
D.concerning on-scene communications