I don't know for sure but I think the second one is an intensive pronoun
Answer:
1) A cardiovascular system is an organ system that conveys blood through vessels to and from all parts of the body, carrying nutrients and oxygen to tissues and removing carbon dioxide and other wastes.
2) "Capillaries connect the arteries to veins. The arteries deliver the oxygen-rich blood to the capillaries, where the actual exchange of oxygen and carbon dioxide occurs. The capillaries then deliver the waste-rich blood to the veins for transport back to the lungs and heart. Veins carry the blood back to the heart."
3) A heart attack is a blockage of blood flow to the heart muscle.
They are all correct but A. Explains it the best
You need to get on top of your stuff.
you need to stay in school and get good grades and if you have a hard time with that then you need to take notes and study. a lot.
you need to focus on your career after college and don't let anyone get in your way or you won't get where you deserve to be.