A medical research team in France recently discovered that

A medical research team in France recently discovered that people with a low risk of heart disease tend to also have low stress levels. The team concluded that a healthy cardiovascular system can protect people from the stress of modern life.

The research team's conclusion depends on which of the following?

A. Medical and pharmaceutical treatments of stress are more effective than psychological treatment.
B. People with high stress levels are more likely to have serious heart disease than are those who have low stress levels.
C. High stress levels do not increase one's chances of suffering from heart disease.
D. Other medical studies indicate that stress levels in citizens of industrialized countries have increased over the last thirty years, as the world becomes increasingly more complex and hectic.
E. People without heart disease also tend to have their blood pressure within an acceptable range.