Blood serum (the antibody-containing fraction of blood is taken from each of five students in a genetics laboratory. Each sample is then tested with red blood cells obtained from each of the other four students. Agglutination of red blood Celts occurs in same sera (designated by a +) but not in others (designated by -). The following table gives the results observed: If the Wood type of student I ls known to be type A, what are the blood types of the remaining four students? Explain your conclusions.