All the traces are（）old ones.

A man was sighted as he fell overboard. After completing a Williamson turn，the man is not sighted. What type of search should be conducted?（）

A.Expanding circle
B.Sector search
C.Parallel track pattern
D.Datum-drift search

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（）the visibility to reduce to one mile by heavy rain，it（）be impossible to rescue the vessel in distress.

A.Was／would
B.Were／would
C.Is／will
D.Is／is to

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