Hemoglobin is found in red blood cells, hemoglobin is globular proteins, which transports oxygen molecules throughout the body. Each hemoglobin protein structure consists of four polypeptide subunits, which are held together by ionic bonds, hydrogen bonds, hydrophobic interactions and van der Waals forces, as well as four heme pigments, one in each of the subunits. These heme groups contain positively charged iron molecules, which can reversibly bind to oxygen molecules and transport them to various areas of the body. Hence, option b is correct.

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