单项选择题
A.at close range B.at end on situation C.at head on situation D.at crossing situation
It is dangerous for vessels without the use of radar（）t...
单项选择题It is dangerous for vessels without the use of radar（）the estuary.
A.to get B.to approach C.to proceed D.to close
Induced magnetism is found in（）.A.hard ironB.soft ironC...
单项选择题Induced magnetism is found in（）.
A.hard iron B.soft iron C.vertical iron only D.horizontal iron only
If several fixed navigational lights are visible at the...
单项选择题If several fixed navigational lights are visible at the same time，each one may be positively identified by checking all of the following EXCEPT what against the Light List?（）
A.Rhythm B.Period C.Intensity D.Color
