Moderate Exercise Is Better Than None, but Excessive Exercise Is

Multiple Choice

Moderate exercise is better than none, but excessive exercise is harmful.What is the shape of the graph of health benefits versus hours of exercise per week if health benefits are measured on the vertical axis and exercise is measured on the horizontal axis?

A) a positively sloped straight line
B) a negatively sloped straight line
C) a vertical straight line
D) a U-shaped curve
E) a hill-shaped curve