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
单项选择题 Induced magnetism is found in（）.
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?（）
单项选择题 How is variation indicated on a small-scale nautical chart?（）
