Final answer:
To start a vehicle with a manual transmission, you must use both feet; the left foot to press the clutch and the right to press the brake.
Step-by-step explanation:
To start a manual transmission vehicle, you need to use both feet. Firstly, you use your right foot to press the brake pedal, ensuring that the vehicle does not move unexpectedly. Secondly, you use your left foot to depress the clutch pedal all the way to the floor. This is necessary to disengage the transmission and allow you to safely start the engine. Once the engine is started, you continue to use both feet to control the vehicle: the left foot remains on the clutch when changing gears, and the right foot moves between the brake and gas pedals as needed for acceleration and slowing down.