Human blood is grouped into ________ main types.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. four.
Human blood is primarily grouped into four main types based on the ABO blood group system: A, B, AB, and O.
These four types are determined by the presence or absence of specific antigens (A and B) on the surface of red blood cells. In addition to the ABO system, blood is also classified by the presence or absence of the Rh factor, which designates blood as either positive (+) or negative (-). Combining these two systems results in the eight common blood types: A+, A-, B+, B-, AB+, AB-, O+, and O-. While there are many other lesser-known blood group systems, the ABO and Rh systems are the most clinically significant for transfusions.