Final answer:
Instinctively, when driving a car or flying in a commercial jet, we use both inertial and non-inertial frames of reference. The car or jet serves as a non-inertial frame during acceleration and as an approximate inertial frame when moving at a steady velocity. Option c is the correct answer.
Step-by-step explanation:
When driving a car, people instinctively use the car itself as a frame of reference. This frame is non-inertial if the car accelerates or takes a turn, as passengers feel a force due to the car's acceleration, a fictitious or inertial force. Nevertheless, some aspects of driving a car also utilize an inertial frame of reference, as the movement of the car can be described relative to the Earth, which is largely considered an inertial frame because it does not undergo noticeable acceleration.
When flying in a commercial jet, passengers may also instinctively use the jet as a frame of reference. However, since a commercial jet usually moves with constant velocity at cruising altitude, it approximates an inertial frame during this time. Still, during takeoffs, landings, or turbulence, the jet becomes a non-inertial frame, similar to a car turning or accelerating.
Therefore, both inertial and non-inertial frames are used instinctively when driving a car or flying in a commercial jet. The correct option is c) Both inertial and non-inertial frames.