Which of below device has the maximum coverage range（）

We took usual steps:sounding the depth, reversing and stopping engine,paying out anchor and 60 fathoms of chain cable in the depth of 12 fathoms.The operation above is（）.

A.berthing
B.searching
C.anchoring
D.picking up pilot

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Which of the following is not a factor which can interfere with the pulse of sound and cause a variation the depth reading?（）

A.salinity
B.temperature
C.the hydrostatic pressure
D.Vessel’s speed

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