Which Phrase Below Describes the Structure of Hemoglobin?
A)either An \alpha

Which phrase below describes the structure of hemoglobin?

A) either an $\alpha$ -globin or a $\beta$ -globin chain
B) an $\alpha$ -globin and a $\beta$ -globin chain
C) two $\alpha$ -globin and two $\beta$ -globin chains
D) three $\alpha$ -globin chains and one $\beta$ -globin chain
E) four $\alpha$ -globin or four $\beta$ -globin chains