At the instant t=0, a train is moving on a straight track with a constant speed of 54km h−1. Along a parallel road, a car starts from rest and accelerates uniformly at 2.0m s−2. Consider the following observers:
(a) a passenger sitting in the train,
(b) the driver of the car,
(c) a person standing on the ground beside the road.
Identify which of these observers are in an inertial frame at t=0. Write only the correct letter(s).