I am no expert but I think the correct answer is C.
That they are <span>caused by microorganisms.</span>
Lack of antibodies because thats the stuff to fight things away
The central element for all living things is carbon, which is why you might often hear the phrase "carbon-based" lifeforms. Another term is often "organic matter"
They are considered to have originated from cyanobacteria through endosymbiosis—when a eukaryotic cell engulfed a photosynthesizing cyanobacterium that became a permanent resident in the cell
