What determines whether an allele is dominant recessive or codominant?

Based on the gene expression for instance if one parent is tall and and one parent is short it depends if the child is tall or short. if the child is tall then tallness is dominant ans shortness is recessive if the child is short that shortness is dominant and tallness is reccesive. however for codominance its a blending or mixture of both alleles. if a white flour and red a flower are mixed and its offspring is pink that is codominance. hope it helps!

Its the 3rd one.

Explanation:

I just answered it..