One round of Edman degradation of the peptide: H2N— Gly—Arg—Lys—Phe— Asp— COOH would result in which of the following structures or their phenyl isothiocyanate derivatives? (A) H2N—Gly—Arg—COOH + H2N—Lys— Phe— Asp—COOH (B) H2N—Gly—Arg—Lys—Phe—COOH + Asp (C) H2N—Arg—Lys—Phe—Asp—COOH + Gly (D) H2N—Gly—Arg—Lys—COOH + H2N—Phe —Asp—COOH