单项选择题

Geographic range is the maximum distance at which a light may be seen under（）.

A.existing visibility conditions，limited only by the curvature of the Earth
B.perfect visibility conditions，limited only by the curvature of the Earth
C.existing visibility conditions，limited only by the intensity of the light
D.perfect visibility conditions，limited only by interference from background lighting

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Due to the shape of the sea anchor，the best way to haul it back aboard is by（）.

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B.getting all hands to assist
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