单项选择题

The proximity of pack ice may be indicated by（）.

A.changes in seawater salinity
B.glare on clouds on the horizon
C.changes in air temperature
D.icebergs

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单项选择题

Small floes of rough，hummocky sea ice capable of damaging a vessel（）.

A.can usually be detected by radar in a smooth sea at a range of 4 to 6 kilometers
B.are indistinguishable from sea return on the PPI
C.are invisible to radar when covered with a thick layer of snow
D.are usually seen at night before they are close enough to provide a radar echo

单项选择题

On a twin-screw，twin-rudder vessel，the most effective way to turn in your own water，with no way on，is to put（）.

A.one engine ahead and one engine astern，with full rudder
B.one engine ahead and one engine astern，with rudders amidships
C.both engines ahead，with full rudder
D.both engines astern，with full rudder

单项选择题

On a single-screw vessel the stern frame（）.

A.furnishes support to the rudder，propeller shaft，and transom frame
B.provides foundations for after mooring winches
C.provides foundations for the main propulsion engines
D.transfers the driving force of the propeller to the hull