Which of the following statements are fundamental to the clonal-selection theory of how the adaptive immune system functions?
I.Each lymphocyte has a unique membrane receptor that recognizes one antigen.
II.When the lymphocyte binds an antigen,it is activated and begins dividing to form many identical copies of itself.
III.Cloned lymphocytes have slight differences and are selected by the spleen for removal if they do not bind an antigen.
IV.Cloned cells descend from an activated lymphocyte and persist even after the pathogen is eliminated.