The primary difficulty is the fact that we do not know all of the organisms that currently exist in the world along with those that existed in the past.
Answer:
Coral polyps, which are animals, and zooxanthellae, the plant cells that live within them, have a mutualistic relationship. Coral polyps produce carbon dioxide and water as byproducts of cellular respiration. The zooxanthellae cells use carbon dioxide and water to carry out photosynthesis.
Explanation:
Answer would be
E
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