Which of the Following Is Characteristic for the Active Sites

Which of the following is characteristic for the active sites of enzymes?

A) Nearly all amino acid side chains of the protein participate in catalysis.
B) The amino acid residues that form the active site are adjacent in the primary structure of the polypeptide.
C) The amino acid residues in the active site that bind the substrate are always the ones that catalyze the reaction.
D) In many cases, the active site changes its conformation when the substrate binds.
E) In many cases, the initial binding of the substrate to the active site involves the formation of a covalent bond.