When reading questions, be careful not to read too quickly. In this case, fast but inefficient reading will lead us to assume that it is asking about ...
C. Webbed feet. I'm pretty sure that's the answer lol
Type O is the remainder after subtracting types A, B and AB.
so percentage of type O blood supply
= 100%-(28+15+10)%
= 100% - 53%
= 47%