What is the unique characteristic of type O- blood?

Type O- blood is known as the universal donor because it can be given to individuals of any blood type without the risk of triggering an immune response. This is due to the absence of A and B antigens on the surface of red blood cells, which are the primary markers that can elicit an immune reaction in recipients with different blood types. Thus, individuals with any other blood type—A, B, AB, or O—can receive O- blood without the risk of hemolytic transfusion reactions, making it especially valuable in emergency situations where there might not be time to test a patient’s blood type.

The other options do not accurately describe the characteristics of type O- blood. For example, being a universal recipient relates specifically to AB blood types, which can accept any blood type due to their universal compatibility. Type O- cannot receive blood from A+ donors due to the presence of A antigens, nor is it only compatible with O+ blood, as O- is actually compatible with all O, A, and B types, both positive and negative.