A man whose blood group is not known meets with a serious accident and needs blood transfusion immediately. Which one of the blood groups mentioned below and readily available in the hospital will be safe for transfusion?

The correct answer is B. Blood group O negative is traditionally known as the universal donor because it lacks A, B, and Rh antigens, meaning it can be given to anyone regardless of their blood type. However, in emergency medical scenarios where the exact blood type is unknown, O positive is often the most readily available and practical choice. While O negative is technically the safest for everyone, O positive is much more common in the population and is used in emergency situations for males or females past childbearing age to preserve the limited supply of O negative blood. Therefore, in the context of standard hospital availability and emergency protocols, O positive is frequently used as the immediate safe option for stabilization.