The purpose of the flywheel of a diesel engine is to ().
A. counterbalance the crank throws on the crankshaft
B. keep the engine running smoothly between power stroke
C. provide a belt-driving surface for the operation of auxiliary machinery
D. prevent the engine from overspeeding
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根据《建筑基坑支护技术规程》(DB11/489-2016)第4.2.2条,对于土质边坡或易于软化的岩质边坡,在开挖时应及时采取相应的排水和坡脚、坡面保护措施。基底设置排水沟时,应离开坡脚不少于()mm,并做好防渗处理。
A. 150
B. 200
C. 300
D. 400
我国的交流电频率为50赫兹。
A. 正确
B. 错误
我国金属矿山多采用自然通风。
A. 正确
B. 错误