Who Should Obtain a Physician's Clearance Before Starting an Exercise

Who should obtain a physician's clearance before starting an exercise program?  

A) Every individual who is beginning an exercise program.
B) Sedentary individuals who are going to perform vigorous exercise.
C) Those who are considered low risk and perform only moderate exercise.
D) Men who are younger than 45 years of age and women who are younger than 55 years of age.