Correct Option: A

Each person’s blood is one of four major types: A, B, AB, or O. Blood types are determined by the types of antigens on the blood cells. Antigens are proteins on the surface of blood cells that can cause a response from the immune system. The Rh factor (Rhesus factor) is a type of protein on the surface of red blood cells. Most people who have the Rh factor are Rhpositive. Those who do not have the Rh factor are Rh-negative. In contrast to the ABO blood group, immunization against Rh can generally only occur through blood transfusion or placental exposure during pregnancy in women.