Not sure if you still need the answer but its number Three, they are the decomposers in many ecosystems
D. He has an aerator that pumps bubbles into the tank
<span>Both photoautotrophs and chemoautotrophs synthesize organic compounds from (inorganic) carbon dioxide, a process known as carbon fixation. Photoautotrophs get the energy to perform these reactions from light. Chemoautotrophs get it from electron donors such as hydrogen sulfide and ammonia. Cyanobacteria, by contrast, convert nitrogen from the atmosphere into ammonia, a process known as nitrogen fixation.</span>
I think the answer is B sorry if I’m wrong