MCQ Detailed View

Human blood is classified into four main groups: A, B, AB, and O, based on the presence or absence of antigens on the surface of red blood cells. Each blood group can be either Rh-positive (+) or Rh-negative (−), which also affects compatibility in blood transfusions.

A person with blood group O negative (O−) is known as the universal donor because their red blood cells lack both A and B antigens and do not have the Rh antigen. This means that their blood does not trigger an immune reaction when transfused into people of any other blood type. Therefore, O group donors can give blood safely to individuals with A, B, AB, or O blood types, especially in emergencies when the exact blood match is not available.

Here’s why the other options are not universal donors:

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  Blood group AB: Known as the universal recipient, can receive blood from all groups but cannot donate to all because it contains both A and B antigens.

  
  


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  Blood group A: Has A antigens, so it cannot donate safely to B or AB recipients.

  
  


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  Blood group B: Has B antigens, so it cannot donate to A or AB recipients.

  
  

However, while O-negative blood can be given to anyone, people with this blood type can only receive blood from other O-negative donors because their immune system may react to other antigens.

In conclusion, option A (O) is the correct answer because individuals with blood group O-negative are called universal donors, making their blood highly valuable for life-saving transfusions in medical emergencies.