A person meets with an accident and needs a blood transfusion but there is no time to check his blood group. Which of the following blood groups could be given to him?

Correct option is B

There are four main blood groups defined by the ABO system. 

• 1. Blood group A - has A antigens on the RBC with anti-B antibodies in the plasma.

• 2. Blood group B - has B antigens with anti-A antibodies in the plasma.

• 3. Blood group AB - has both A and B antigens, but no antibodies.

• 4. Blood group O - has no antigens, but both anti-A and anti-B antibodies in the plasma.

• Red blood cells sometimes have another antigen, a protein known as RhD antigen. If this is present, the blood group is RhD-positive. If it is absent, the blood group is RhD-negative. In most cases, ORhD-negative blood (O–) can safely be given to anyone. 

• It is often used in medical emergencies when the blood type isn't immediately known. It's safe for most users because it doesn't have any A, B or RhD antigens on the surface of the blood cells, and is compatible with every other A,B,O and RhD blood group.