C. Reproductive because the circulatory assists the runner in pumping blood into his body, his muscular is the muscles the runner uses to run, and the skeletal supports the muscles and the rest of the body while he is running. The reproductive system isn't actively being used during this time
Answer:
B option is correct answer.
Explanation:
As we know that there are 2 types of metabolic reactions in which one is anabolic mean 'building up" as in your question anabolic is mentioned but the second type you ask and the answer of your question is the catabolic means" "breaking down"
It's called the cell membrane, it can control what substance can go in and out of cell.
The answer is 51,200 bacterium.