Final answer:
Type O negative blood is considered the universal donor as it can safely be transfused into individuals with any blood type, while Type AB positive blood is known as the universal recipient because it can be received from all donors.
Step-by-step explanation:
The universal donor blood type is Type O negative (O-). This blood type is called the universal donor because it lacks A and B antigens on the surface of the red blood cells, preventing an immune response when it is given to individuals with different blood types. In contrast, Type AB positive (AB+) blood is referred to as the universal recipient, as those with this blood type have both A and B antigens and do not produce anti-A or anti-B antibodies, allowing them to safely receive blood from any donor. However, it is always best to match exact blood types for transfusions when possible to avoid complications related to other factors such as the presence of Rh antibodies.