Final answer:
In a multiple cylinder gasoline engine, the device that triggers ignition at the beginning of each cylinder's respective power stroke is the spark plug.
Step-by-step explanation:
In a multiple cylinder gasoline engine, the device that triggers ignition at the beginning of each cylinder's respective power stroke is the spark plug. The process of ignition involves the spark plug delivering a spark to the air-fuel mixture, creating a small explosion which increases the temperature and pressure within the cylinder. This expansion exerts force on the piston, contributing to the power output of the engine. The correct answer to the question is option (c) spark plug.