ANS:A - engine having carburettor.

A spark plug is provided in a/an engine having a carburetor. A spark plug is an essential component of gasoline (petrol) engines, which typically use a carburetor or fuel injection system to mix air and fuel before it enters the engine cylinders. The spark plug ignites the air-fuel mixture in the combustion chamber, initiating the combustion process that powers the engine. On the other hand, diesel engines do not require spark plugs for ignition. Diesel engines rely on the compression of air in the cylinders to generate high temperatures, which causes the injected diesel fuel to ignite spontaneously (compression ignition) without the need for a spark. Therefore, spark plugs are specifically provided in engines with carburetors or fuel injection systems, typically found in gasoline (petrol) engines, and are not used in diesel engines, which rely on compression ignition.