单项选择题
To obtain accuracy in fixing by DF，（）and three stations should be used.
A.parallel bearings B.long-range bearings C.short-range bearings D.cross bearings
单项选择题 Vessels in port may use（）for receiving typhoon warnings during the typhoon season.
单项选择题 We’ll see（）the compasses are in good condition.
单项选择题 More exact assessment of visibility when（）is used to determine the range of vessel or other objects in the vicinity.
