I think the main cause would be water
1.
C. Genus and species
Binominal nomenclature: a formal system of naming species of living things, such as humans which are <em>homo sapiens.</em>
2.
A. carbohydrates
any of a large group of organic compounds occurring in foods and living tissues and including sugars, starch, and cellulose.
3.
C. work with other cells
one unicellular organism would quickly die if was not within a colony of very similar unicellular organisms.
4.
C. Bacteria
bacteria are able to cause contagious diseases seeing as a virus, (which can be a contagious disease) is a form of bacteria.
Humus is a dark organic matter that is an important part of your soil
Humus consists of decomposing organic material. The process of creating humus is called Humification: decomposition of o<span>rganic matter into smaller and smaller molecules by the micro-organisms in the soil (mostly bacteria and fungi).</span>
NUCLEAR FUSION, hope it helps