Answer: B) Ecologist
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Step-by-step explanation:
A professor could mean any other person explaining how the health of coral reefs affects ocean animals. But it's not their specialty.
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Ecologists "study these relationships among organisms and habitats of many different sizes, ranging from the study of microscopic bacteria growing in a fish tank, to the complex interactions between the thousands of plant, animal, and other communities found in a desert. Ecologists also study many kinds of environments."
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A Chemist doesn't really mean anything involving marine animals or the problem.
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A visitor can have some knowledge about the problem but are clueless.
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So the most logical answer would be B) Ecologist
Sorry, I didn't explain it as well but it's the best I can do, Good luck with your test.