61. A mixture of four amino acids is separated by using a cation exchanger with an elution gradient of increasing NaClsolution. What is the correct elution sequence?
(A) Asp, Lys, Arg, Ser
(B) Asp, Ser, Lys, Arg
(C) Asp, Arg, Ser, Lys
(D) Ser, Asp, Arg, Lys
(E) Lys, Arg, Ser, Asp