The answer to this is C. Industry. It's the only man made factor.
Answer: "photosynthesis" .
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<u>Note</u>: These small, moving "green disks" seen while observing an <em>Elodea</em> plant cell—under a microscrope— are "chloroplasts". The "chloroplasts" are organelles that ar responsible for "photosynthesis" .
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A is the correct answer to the question