Hi, can I have help with number 45? Thank you

Hemoglobin is the protein pigment present in red blood cell responsible for carrying almost all oxygen in the blood. Each molecule of hemoglobin binds with 4 oxygen molecules and the reaction is reversible. WBC is the one responsible for carrying oxygen to all organs of the body. Platelet is responsible for clotting blood. Lymph nodes play as a filtering agent present in the lymphatic fluid that are responsible for fighting infection.
Answer - b. hemoglobin in red blood cells