Final answer:
The most common blood type in the U.S. population is type O. This blood type is known as the universal donor and it is the most prevalent in the population, with about 43 percent of people having this blood type.
Step-by-step explanation:
The most common type of blood in the U.S. population is type O. The ABO blood group system classifies blood types based on the presence of specific antigens on the surface of red blood cells. People with type O blood are considered universal donors because their red blood cells do not have A or B antigens, hence there is no risk of an immune response when their blood is transfused into a person with a different blood type. Furthermore, data from organizations like the American Red Cross and United Blood Services indicate that the prevalence of type O blood in the population is approximately 43 percent, making it the most common blood type.