Final answer:
The qualitative change during a race is the increase in heart rate, which is related to the body's physiological response to exertion.
Step-by-step explanation:
The qualitative change during the race is c) Heart rate increase. Unlike the time taken to finish, distance covered, or the runner's height, the heart rate increase is not measured in numerical terms but rather describes how the body responds to the physical exertion of the race. This is related to the physiological changes that occur in a runner's body, which include the responsiveness and movement of the runner demonstrated during the race, as well as the body's ability to coordinate muscle groups and manage internal body temperature through sweating.