This document analyzes blood typing results from 4 patients and asks the reader to answer questions about blood types and compatibility. Table 1 shows the results of blood serum tests for the 4 patients, identifying their blood types as A+, B-, AB+, and O-. Subsequent questions ask the reader to determine blood type compatibility for transfusions based on these results, compare features of agglutinogens and agglutinins, describe how blood typing is performed, and discuss uses and safety considerations for blood typing.