Blood group of an individual is determined by

Correct answer: (d) None of the above

Explanation

A person's blood group is set by the antigens on the surface of the red blood cells (A, B, both or neither), which are controlled by genes inherited from the parents (three alleles: I^A, I^B and i).

Haemoglobin, the WBC–RBC combination and the shape of RBCs do not decide it, so the answer is "None of the above".