Question

What begins the combustion phase of a four-stroke engine cycle?

A. The air-fuel mixture is compressed.
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B. An air-fuel mixture flows into the cylinder.
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C. The air-fuel mixture is ignited.
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D. The air-fuel mixture expands.

Answer 1

Answer: B

Explanation: The engine cycle begins with the intake stroke as the piston is pulled towards the crankshaft (to the left in the figure). The intake valve is open, and fuel and air are drawn past the valve and into the combustion chamber and cylinder from the intake manifold located on top of the combustion chamber.