What tool is used to remove the spark plug during disassembly?

The tool used to remove a spark plug during disassembly is a 5/8" spark plug socket. This specialized socket is designed to accommodate the specific size and shape of most spark plugs, allowing for a secure grip while ensuring that the connector on the end of the spark plug is not damaged during removal. The deep well of the spark plug socket further facilitates access to spark plugs that may be seated deep within the engine, providing added leverage and support.

In contrast, a 1/2" socket wrench is a more general tool that does not fit the spark plug properly and lacks the necessary depth for effective use. A flathead screwdriver is not suitable for this task as it cannot provide the necessary grip or torque needed to unscrew a spark plug. Lastly, a 10-millimeter ratchet is also not compatible with standard spark plugs, which require either a 5/8" or 13/16" size socket, depending on the engine. Therefore, the 5/8" spark plug socket is the right choice, making it the correct answer for this question.