单项选择题
When sailing in cold zones, the（） should be drained of water.
A.the ventilation pipe B.the water line for fire fighting on the deck C.the fuel oil line D.the water supplying line in bath room
单项选择题 When sailing in cold zones, the（） should be heated.
单项选择题 When the ships is going to enter into the harbor,（）.
单项选择题 Most often （） is attached to the engine-propeller shaft for efficient electric power generation.
