Bacteria should be it
you didnt include the multipule choice answers so this is a guess but it should be correct
I might be wrong but i think its T
Answer: <u>Both</u> are important.
Explanation: Carbon dioxide, also called CO2, is found in water as a dissolved gas. It can dissolve in water 200 times more easily than oxygen. Aquatic plants depend on carbon dioxide for life and growth, just as fish depend on oxygen. Plants use carbon dioxide during the process of photosynthesis. So therefore, they are both important for survival. Plants need carbon dioxide and other organisms (animals and humans) need oxygen. Hope this helps ^-^.
