The correct answer is: D. exercising
This happens because, when you exercise, the blood vessels in your muscles dilate (vasodilation) and as a consequence, the rate of blood flow is faster. The increased blood flow delivers more oxygenated blood to the working muscle.
B. confirmed that learning causes neurological changes in the brain
Understanding evolution helps us solve biological problems that impact our lives. There are excellent examples of this in the field of medicine. To stay one step ahead of pathogenic diseases, researchers must understand the evolutionary patterns of disease-causing organisms. To control hereditary diseases in people, researchers study the evolutionary histories of the disease-causing genes. In these ways, a knowledge of evolution can improve the quality of human life.




Well, nitrogen is the gas that makes up 78% of the earth's atmosphere.
I would guess its in the air that we breathe. I am not really sure. Just basing this answer off of research.