1. a passenger in the rear seat of a car moving at a steady speed is at rest relative to

A passenger in the rear seat of a car moving at a steady speed is at rest relative to the front seat of the car.

Explanation: From the Newton's first law, if the object is moving with uniform speed or if the object is in a state of rest then it will remain in that state unless it is acted upon by the external force.

In the given situation, a passenger in the rear seat of a car moving at a steady speed is at rest relative to the front seat of the car because the front seat of the car is also at rest in the car relative to the passenger. Only the car is moving.

Therefore, a passenger in the rear seat of a car moving at a steady speed is at rest relative to the front seat of the car.