Which cells of the skin are filled with a tough, fibrous protein and account for most of the epidermal cells of the skin?

After hydrogen and oxygen, witch element makes up almost all of the most common substance in your body

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.

In the practice of science, this type of reasoning is used to develop explanations.