Why Do the Blood Types of a Person Providing Blood

Why do the blood types of a person providing blood for a transfusion,and the person receiving the blood,have to be of a compatible ABO type?

A) This assures that the DNA matches between the two individuals,thus avoiding problems with genetic conflict later in life.
B) This assures that there will not be an antibody-antigen reaction,in which the red blood cells with the "dominant" A or B alleles engulf the red blood cells with the "recessive" (O) alleles.
C) This assures that antigens of one type of blood cell do not attract the notice of the antibodies in the recipient's blood stream.
D) This assures that a methylation effect will not occur between the two sets of blood cells.