A driver's license is required for which of the following?

A driver's license is essential for certain activities related to operating a vehicle, and the correct option indicates that both sitting in the driver's seat with the engine running and steering a car being pushed or towed require a valid driver's license.

When you sit in the driver's seat of a car while the engine is running, you are in a position to control the vehicle. This scenario implies that the vehicle is operable, and thus possessing a driver's license is necessary to ensure that the person driving has been tested for the skills and knowledge needed to operate a vehicle safely on the road.

Similarly, when steering a car that is being pushed or towed, even though you may not be driving it in the conventional sense, you are still in a position of control over the movement of the vehicle. This may affect where the vehicle ends up and its interaction with other vehicles and pedestrians on the road. For safety and regulatory purposes, being licensed ensures that the person steering understands the respective laws and safety requirements.

Both situations warrant the requirement of a driver's license to ensure responsible vehicle operation and adherence to traffic laws.