Suppose you counted 1000 offspring from cross (iii), and 800 of the offspring had either a gray body with normal wings OR a black body with vestigial wings. From this you should conclude that
A. the two genes are on the same chromosome, 20 map units apart
B. the two genes are on the same chromosome, 80 map units apart
C. alleles of the two genes assort independently
D. the genes are both on the X chromosome
E. something went wrong in your experiment