You have isolated a new protease that cleaves peptide bonds on the carboxyl side of Asp and Glu. Based on the enzyme's inactivation by DIFP, you suspect that it may utilize a mechanism similar to chymotrypsin. The difference in specificity might be explained by

A.) the presence of a positively charged residue in the S1 binding pocket.

B.) the presence of a negatively charged residue in the S1 binding pocket.

C.) replacement of serine-195 with a positively charged residue.

D.)the absence of the S1 binding pocket.