Which Statement About Willpower Is Accurate

Which statement about willpower is accurate?

A) In general, people have far more willpower than they think they do.
B) Most people actually tend to decrease in willpower as they age.
C) People who practice willpower "exercises" develop stronger levels of willpower in the long term.
D) People show very different levels of willpower depending on the domain (eating behavior, work behavior, criminal behavior, etc.)