Chymotrypsin Has a Large Specificity Pocket to Bind the Aromatic $\rarr$

Chymotrypsin has a large specificity pocket to bind the aromatic amino acids while elastase has a very small specificity pocket meant to bind Ala or Gly. Which of the following amino acid substitutions changes the specificity pocket of chymotrypsin to that of elastase?

A) Trp $\rarr$ Ser
B) Leu $\rarr$ Ala
C) Gly $\rarr$ Val
D) Lys $\rarr$ Asp
E) Val $\rarr$ Asn