单项选择题
A.clean report
B.serious deficiencies
C.clear ground
D.detention report
单项选择题 If a ship is proceeding towards the magnetic equator，the uncorrected deviation due to permanent magnetism（）.
单项选择题 How does an icebreaker normally free a ship which has become beset while navigating independently?（）
单项选择题 Every vessel should at all times proceed at a safe speed. Safe speed is defined as that speed where（）.