What are the most abundant organisms in any given ecosystem? Justify your answer

Pelagibacter ubique is often cited as the most common organism ever: it's a third of all the single-celled organisms in the ocean. But, as is always the case, something eats P. unique. In fact, four different viruses parasitize this one species.

Explanation:

Bacteria are monerans, the simplest single-celled organisms. They are the smallest of all cells, visible only through powerful microscopes. Bacteria are also the most abundant forms of life. ... Bacteria recycle nutrients in the soil and aid the human digestive system.

segmentation=endoskeleton=backbone=coelom=tissues

c should be the answer