A group of science students have been learning how the human circulatory system reacts during exercise. The students measured their heart rates both before and after they ran five laps around the school gym. This was repeated two more times, with a 5 minute rest period between each trial. The average heart rates of the students are shown in the bar graph. Which of the following correctly states the general relationship between exercise and heart rate in humans

Which of the following correctly states the general relationship between exercise and heart rate in humans

A. Exercise lowers a person's heart rate

B. Exercise will increase a person's heart rate

C. The heart rate was highest in trial 2

D. There is no relationship between the average heart rate and exercise