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
相关考题
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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 -
单项选择题
In selecting a tug for moving a vessel，consideration should be given to its（）.
A.indicated horsepower，bollard pull，and displacement
B.indicated horsepower，maneuverability，and displacement
C.indicated horsepower，bollard pull，and maneuverability
D.bollard pull，displacement，and maneuverability
