What are three types of a nucleotide?

How did the research presented in the article affect scientists' understanding of the evolution of eukaryotes

Which is an advantage of having memory cells when a pathogen is encountered for a second time. a) the memory cells are what proliferate into clones of cells in response to the binding of an antigen. b) memory cells are vital to the primary immune response in that they immediately recognize pathogens even at the first encounter. c) memory cells are essentially effector cells that are short lived and attack antigens even without having a receptor specific to that antigen. d) it ensures that more lymphocytes with a receptor specific to a particular antigen will be present than in a host that had never encountered that pathogen.

Actinobacteria sp. are fermenting organisms (which do you use oxygen to breathe) referred to as chemoorganohetereotrophs this means they break down organic material and convert it to inorganic material. which part of the carbon cycle does this describe