A : a car driving down a hill
        
             
        
        
        
Answer:
b.  Capillaries; veins; arteries
Explanation:
Capillaries are the blood vessels with very thin walls. They serve as a site for an exchange of substances such as respiratory gases, nutrients, and toxins between the blood and the cells of the tissues. Veins are the blood vessels that mostly pick the deoxygenated blood from the body cells and deliver it to the heart for oxygenation. On the other hand, arteries are the blood vessels that mostly carry the oxygen-rich blood. They pick the oxygenated blood from the heart and deliver it to body cells. Therefore, veins carry blood towards the heart while arteries carry it away from the heart. 
 
        
             
        
        
        
The three major factors that can contribute significantly to a project success are (1) timely user involvement, (2) executive management support, and (3) a clear user requirements. There are other success criteria, but with these three elements in place, the chances of success are much greater 
(Do whatever you want with this information lol, but honestly I hope this helps)