Concept:Blood group is determined by specific antigens present on the surface of red blood cells (RBCs), not by haemoglobin, WBC/RBC combination, or RBC shape.
Explanation:The ABO system depends on A and B antigens. Type A has A antigen, type B has B antigen, type AB has both, type O has neither.
The Rh system depends on the D antigen. If present, blood type is Rh-positive; if absent, it is Rh-negative.
Thus, blood group is based solely on these antigens.
Option A (haemoglobin) is incorrect – haemoglobin carries oxygen.
Option B (combination of WBC and RBC) is incorrect – blood group is not about cell counts.
Option C (shape of RBC) is incorrect – shape is related to disorders like sickle cell anemia, not blood group.
Therefore, none of the above options correctly describe what determines blood group.
Answer:Option D: None of the above