Which of the Following Is Not a Proven Barrier to Increasing

Which of the following is not a proven barrier to increasing health promoting behavior?

A) middle-aged and older people today expect less benefit from exercise than do younger people
B) lifelong sedentary habits and a negative attitude toward exercise
C) older people believing in the traditional idea that you shouldn't fight nature, and one must learn to grow old gracefully
D) lack of information about the causes and cures of illness