28. Five students are discussing a peptide consisting of nine amino acid residues. Student A: When this peptide is digested by chymotrypsin, you can get a tripeptide and a hexapeptide. Student B: This peptide cannot be cut by cyanogen bromide. Student C: This peptide does not contain any amino acids with two chiral centers Student D: When this peptide is digested by trypsin, you can get a tripeptide and a hexapeptide. Student E: When I dissolved the peptide in 100 mM phosphate buffer (pH 7), this peptide is positively charged. What might be the peptide sequence? (A) MSEFAHKVW. (B) SERLLWATK. (C) QGEKCYIPC. (D) FHRGPWSSM. (E) CSKQAYNDR.