单项选择题 Due to the large amount of heat picked up by the air in boiler and engine rooms, it would be （） to maintain ambient conditions within the comfort zone by air conditioning.

单项选择题 A(n) （） is a mechanical attack on the metal surface which may be due to a disturbance in the flow of the water over the blade of the propeller.

单项选择题 A (n) （） is a chemical or electro-chemical attack on the metal surface which may be further increased if the sea-water is polluted.