10. how does regular exercise improve cardiovascular function during times of stress

It increases oxygen supplies and lowers triglyceride levels. 

Hope this helps. 
(:

According to my research I found questions similar to this with answers:

A) It increases the level of hormones circulating in the body
B) It reduces the amount of endorphins released in the body
C) It reduces carbon dioxide supplies and raises triglyceride levels 
D) It increases oxygen supplies and lowers triglyceride levels.

Among the following choices the answer would be D) because exercise also helps keep your mind off stress since without anxiety slowing you down, you can focus on burning those calories.