Final answer:
In a contact type ignition system, the spark plug is part of the primary circuit of the ignition system.
Step-by-step explanation:
In a contact type ignition system, the spark plug is part of the primary circuit of the ignition system. The primary circuit includes the battery, ignition switch, ignition coil, distributor, and the spark plug. The battery provides the power to the primary circuit, and when the ignition switch is turned on, it activates the ignition coil, which generates a high voltage spark that is delivered to the spark plug.