The graph represents the acceleration of two cars, accel 1 and accel 2, during a road trip. which statement best describes the differences between the two cars' acceleration during the trip?
a) accel 1 accelerates throughout the entire trip; accel 2 does not accelerate during the trip.
b) accel 1 rapidly accelerates and then stops; accel 2 maintains a constant velocity during the trip.
c) accel 1 has a constant rate of acceleration; accel 2 accelerates at different rates during the trip.
d) accel 1 accelerates for the first two-thirds of the trip; accel 2 has a constant rate of acceleration.