正确答案: B

reducing friction

题目：A lubricant often has to perform many duties in any situation, in addition to its fundamental job of （）.

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学习资料的答案和解析：

[单选题]关于废气锅炉烟垢着火温度（）。Ⅰ.烟垢潜在着火温度一般为300—400℃；Ⅱ.存在未燃烧的燃油时烟垢着火温度约为150℃；Ⅲ.极端情况下甚至低到120℃仍可发生烟垢着火

Ⅰ+Ⅱ+Ⅲ

[单选题]The main bearing shells often have a thin （） of lead or indium to provide a layer giving protection against corrosion.

flash

[单选题]Exhaust valve grooving and corrosion is caused by certain components of residual fuel oilThese components are sodium, sulfur, and （）.

vanadium

[单选题]If your propeller is racing in rough weather，you should（）.

decrease your engine speed