[单选题]Proper lubrication of the main bearings is more easily obtained in a single acting, four-stroke/cycle diesel engine than in a tow-stroke/cycle diesel engine because________.

正确答案 ：A

The direction of pressure on the journal in four-stroke engine is continuously

[单选题]硅胶管消毒灭菌不能用：

正确答案 ：D

70%酒精浸泡

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