Answer:B
Step-by-step explanation:
Each hemoglobin molecule has four globin chains (in hemoglobin A, the predominant form in adults, the hemoglobin molecule includes two alpha and two beta chains). Each globin chain is associated with one heme group, containing one atom of iron. Each of the four iron atoms can bind loosely with one molecule (two atoms) of oxygen. Thus, each hemoglobin molecule can transport eight oxygen atoms.