Invariant Amino Acids in a Protein Are Presumed

Invariant amino acids in a protein are presumed:

A) To be unimportant in the structure and function of the protein
B) To be essential to the structure and function of the protein
C) Always to occur at the beginning of the amino acid sequence of an enzyme
D) Always to occur at the end of the amino acid sequence of an enzyme
E) To be part of the prosthetic group