单项选择题
A.is used mostly by towing vessels
B.has a maximum depth of 14 feet (4.3 meters) at MHW
C.West Gap has a controlling depth of 24 feet
D.is entered through the East Gap or the West Gap
单项选择题 One method of controlling rats on vessels is by rat-proofing. Rat-proofing is accomplished by （）.
单项选择题 Multi-year ice is the hardest sea ice and should be avoided if possible. It is recognizable because of what tone to its surface color? （）
单项选择题 In order to benefit from the use of storm oil in heavy seas，the storm oil should be spread （）.