Correct option is C
Pre-ignition: This occurs when the air-fuel mixture ignites before the spark plug fires, often due to a hot spot (like an overheated spark plug tip, carbon deposits, or exhaust valve). A hot spark plug can indeed cause pre-ignition.
Post-ignition: This is not a standard term in engine terminology. It might be a distractor or misinterpretation. Typically, we have "ignition" (normal spark) and "pre-ignition" (abnormal early ignition). "Post-ignition" doesn't refer to a recognized phenomenon caused by a hot spark plug.
Detonation: Also known as engine knock, this occurs when the air-fuel mixture explodes unevenly (multiple flame fronts) after normal ignition. A hot spark plug can contribute to detonation indirectly by causing pre-ignition, which may lead to detonation, but it is not a direct cause. However, detonation is primarily caused by factors like low-octane fuel, high compression, or advanced ignition timing—not directly by a hot spark plug itself. But note: a hot spark plug can create conditions that promote detonation.
Run-on-ignition: Also called "dieseling," this occurs when the engine continues to run after the ignition is turned off, due to hot spots (like carbon deposits or hot spark plugs) igniting the mixture. A hot spark plug can cause run-on.
