During a 3-hour trip, a car’s trip computer reports an average speed of 55 mph. At exactly t=2.5 h, the speedometer reads 70 mph. Which of the following statements best interprets these two pieces of information?
(a) The car’s speed has been close to 70 mph for most of the trip because its instantaneous speed exceeds the average.
(b) An average speed of 55 mph guarantees that the car never exceeded 55 mph at any moment.
(c) Because the instantaneous speed is greater than the overall average, the car must have been traveling at some speed less than 55 mph at another time during the trip.
(d) To balance the 70 mph reading at t=2.5 h, the car had to be traveling below 55 mph immediately before t=2.5 h.