Which component is responsible for igniting the air-fuel mixture in gasoline engines?

• A. Crankshaft
• B. Spark plug
• C. Fuel injector
• D. Cylinder head

Answer: (B)

The spark plug is the component responsible for igniting the air-fuel mixture in gasoline engines. It generates a high-voltage electrical spark that occurs at precisely the right moment during the engine's cycle, allowing combustion to take place. This ignition is crucial for the engine's performance, as it initiates the burning of the air-fuel mixture in the combustion chamber, leading to the power stroke that drives the engine’s pistons.

In contrast, while the crankshaft is an essential component that converts the linear motion of the pistons into rotational motion, it does not play a direct role in the ignition process. The fuel injector is responsible for delivering the correct amount of fuel into the intake system or combustion chamber, but it does not itself ignite the fuel. The cylinder head serves as the cover for the combustion chamber and contains various components, including the spark plugs, but does not itself ignite the air-fuel mixture. Thus, the spark plug is the key component that ignites the mixture, making it the correct answer.