We need blood because it carries oxygen and helps us sustain life. The organ that pushes blood through the body is the heart.
I dont want to mislead you, but I believe the answer is A because letter B is wrong because plants go through cellular respiration and photosynthesis, whereas animals go through cellular respiration but not photosynthesis, and for C, I've never heard of that so it doesnt seem likely.
It is converted into Carbon dioxide which is given off as a waste product
Yes because if there is too much vegetation and not enough omnivores or herbivores the carnivores could eat all other animals and the eventually go extinct because of food loss and starvation. <span />