How Has Our Knowledge About the Heart's Ability to Pump

How has our knowledge about the heart's ability to pump blood as the body ages changed in recent years?

A) We used to think that blood capacity was maintained in old age as the heart weakened but the arteries thinned.
B) We used to think that blood capacity was affected only by stress and diet,but now we know it is affected by aging as well.
C) We used to think that blood capacity decreased only in adults who were unhealthy,but now we know that it decreases for everyone.
D) We used to think that blood capacity decreased in all elderly adults,but now we know that heart capacity can be maintained with healthy habits.