[主观题] 【翻译】在新型发动机上，每个活塞有三个活塞环。（在老式发动机上，每个活塞有四个甚至五个活塞环）环的内侧装在活塞的环槽里，环的外表面紧压在气缸壁上。

1、[单选题]Spark timing is so critical to an engine’s performance that most modern cars use a sensor to tell the engine control unit(ECU) __ .
l.

• A、the exact temperature of the spark plugs.
• B、the exact position of the pistons.
• C、 the exact location of the coi

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2、[主观题]【翻译】As the camshaft rotates, the lobe, or high spot of the cam, pushes against parts connected to the stem of the valve. This action forces the valve to move downward. This action could open an inlet valve for an intake stroke, or open an exhaust valve for an exhaust stroke.

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3、[主观题]【翻译】润滑系的机油泵从油底壳抽出机油 并把机油输送给发动机的所有工作部件。机油从油底壳流进流出.因而在油底壳和发动机的工作部件之间就有机油定向循环流动。

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4、[主观题]【翻译】大多数活塞由铝铸造而成。通过连杆的作用，活塞把可燃混合气燃烧产生的力传递给曲轴，带动 曲轴旋转。

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5、[主观题]【翻译】The engine block serves as a rigid metal foundation for all parts of an engine. It
contains the cylinders and supports the crankshaft and camshaft. In older engines, the
valve seats, ports, and guides are built into the block. Accessory units and the clutch
housing are bolted to it. Blocks are made of either cast iron or aluminum. The lighter

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