21. Which of the following statements regarding immunoglobulin light chains is correct?
(A) k (kappa) associates with only particular heavy-chain isotypes
(B) Agiven antibody may contain just k (kappa), or justλ (lambda), or both
(C) Most antibodies in humans contain 2. (lambda) light chains
(D) There is no functional difference between x (kappa) andλ (lambda)
(E) Light chains possess only framew work regions, not hypervariable regions