Final answer:
A driver's license is required for I. Sitting in the driver's seat of a car while the engine is running.
Step-by-step explanation:
A driver's license is essential when operating a vehicle under one's control, such as sitting in the driver's seat with the engine running (scenario I). This license ensures that an individual possesses the necessary skills, knowledge, and legal authorization to operate a motor vehicle safely on public roads.
However, scenario II, steering a car while it's being pushed or towed by another vehicle, doesn't necessitate a driver's license as the vehicle is not under its own power, and the driver isn't in control of its movement. In the first scenario, even without actively driving the car, being in the driver's seat with the engine running poses the potential for the vehicle's immediate movement, thus requiring the driver to hold a valid license to operate it.
Correct answer: I. Sitting in the driver's seat of a car while the engine is running.