单项选择题
With regards to a diesel engine crankcase explosion, the most violent is the（） (1) primary explosion (2) secondary explosion
A.(1) only B.(2) only C.both (1) and (2) D.neither (1) or (2)
单项选择题 Waterside scale in a fire-tube boiler may cause （）.
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 （）.
