单项选择题
Waterside scale in a fire-tube boiler may cause （）.
A.increased heat transfer B.fireside erosion C.high steam demand D.overheated tubes
单项选择题 The maximum pressure developed by a waste heat boiler is determined by the main engine exhaust （）.
单项选择题 Camshafts are usually driven by timing gears or （）.
单项选择题 A waste heat boiler is installed on some diesel propelled vessels to （）.
