In medicine, blood type is the classification of red blood cells by the presence of specific substances on their surface. In the early part of the 20th century, physicians discovered that blood transfusions often failed because the blood type of the recipient was not compatible with that of the donor. In 1901 the Austrian doctor Karl Landsteiner classified blood types and discovered that the hereditary blood factor is of great importance in blood transfusions because it creates reactions that can threaten the life of newborn infants.
The four blood types are known as A, B, AB, and O. Blood type A contains red blood cells that have a substance A on their surface. This type of blood also contains an antibody directed against substance B, which can be found on the red cells of persons with blood type B. Type B blood contains the opposite things. Blood type AB contains neither antibody, but red cells in this type of blood contain both A and B substances. In type O blood, neit
A. his father or his mother
B. his mother and his father
C. his grandparents
D. himself
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