Final answer:
A car driving in a circle at a constant speed is accelerating because it constantly changes direction, resulting in centripetal acceleration. So the correct option is A.
Step-by-step explanation:
The object that is accelerating among the choices provided is A) A car driving in a circle at a constant speed of 35 mph. Acceleration refers to a change in velocity, which includes changes in either speed or direction. Although this car maintains a constant speed, the direction is constantly changing as it moves in a circle, resulting in a centripetal acceleration towards the center of the circle. All the other options describe motion in a straight line at a constant speed, where neither the speed nor the direction is changing, so these are not cases of acceleration.
Acceleration can occur in three main ways: by speeding up, slowing down, or changing direction. The car driving in a circle at a constant speed is accelerating because of the change in direction, even though the speed remains unchanged.