Why does incomplete dominance not support the blending theory of inheritance?

answer; a male inherits only one allele of the x-linked gene controlling hair color;

the cladogram shown here shows similarities and differences among several classes of vertebrates. anatomically, the four have limb structure as their common ancestor. we might separate the mammals from the other three classes because they a) divergent; do not lay eggs b) identical; are warm-blooded c) varied; a four chambered heart d) homologous; have mammary glands