If All of the Cysteine Residues of a Protein Were

If all of the cysteine residues of a protein were changed to threonines,

A) the structure of the protein would not change, because both residues have hydrophobic properties.
B) the protein would lose activity, but the structure would remain the same.
C) the protein would lose peptide bond formation, and thus it would lose its primary structure.
D) the protein would lose disulfide bond formation, which would affect the stability of its tertiary structure.
E) the hydrogen bonds would be lost, affecting α helix and β pleated sheet formation.