A.<span> Air pollution............................</span>
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I believe the answer is : A - Evolution
Good luck!
The answer is D, for when one tropic level is eaten by the tropic level above it, the tropic level is supporting the higher one. I. E. Rabbits are supported by the grass because rabbits eat the grass. Also, the grass population would be larger than rabbits, the rabbits larger than snakes, so on and so forth, so B is ruled out. B states that each population is larger than the one BEFORE it, but there is no way there would be more rabbits than grass. Also, there are both herbivores and carnivores in the food chain, so A and C are out. The best answer is D.
The major organ of the circulatory system that causes blood to flow through the body by its pumping action is the heart.
