In rabbits, a dominant gene produces spotted body color, and itsrecessive allele solid body color. Another dominant gene produces short hair, andits recessive allele long hair. Rabbits heterozygous for both characteristics weremated with homozygous recessive rabbits. The results of this cross were as follows:48 spotted, short hair; 144 solid, short hair; 156 spotted, long hair; 52 solid, longhair.   What is the map distance between the two genes?

A. 25 m.u.
B. 75 m.u.
C. 50 m.u.
D. 12.5 m.u.
E. none of the above