That would be like your...height, skin color and eye color ect...
Abstract would be the answer
Answer:
The reason is because the heart requires more oxygen when exercising. Several physiological events happen to increase the blood flow and therefore oxygen flow to that muscles,including the heart.
Also the volume of blood that the heart pumps out is maintained so that the body organs receive the necessary amount of oxygen and nutrition, because if it didn't adjust the flow of blood to match activity level, you will be insufficient. Either output method will be lower than needed.
1/2 I think because it is supposed to be 50% which is basically 1/2.
Pretty confident that it is A, judging by that the word composition is used as a combination or a ratio of 2 things. Also none of the other options make sense.
