Which of the following statements about hemoglobin is NOT TRUE:

A) The most common form of hemoglobin in the adult is $\alpha$ ₂ $\beta$ ₂
B) Hemoglobin has four chains and four heme groups
C) Heme groups in hemoglobin consist of porphyrin ring and an Fe atom
D) Breakdown of hemoglobin produces one bilirubin molecule per hemoglobin molecule
E) Sickle cell anemia results from a single amino acid substitution in the $\beta$ chain