Hemoglobin Contains Four Polypeptide Chains Per Molecule

Multiple Choice

Hemoglobin contains four polypeptide chains per molecule. As individual items, and with no other information, the best evidence for this conclusion is

A) hemoglobin contains four iron atoms per molecule.
B) a molecule of hemoglobin binds four atoms of oxygen.
C) hemoglobin crystallizes in the cubic crystal form.
D) the molecular weight of hemoglobin is 64,000.
E) there are four N-terminal valine residues per molecule of hemoglobin.