Two pure-breeding mutant plants produce white flowers. when they are crossed, all of the progeny have wild-type purple flowers. What does this genetic complementation test tell you?

A. The geners are part of distinct biosynthetic pathways

B. the two lines exibit different mutations in the same gene

C. more than one gene is involved in determining the phenotype

D. the allele is pleiotropic

E. The allele exhibits incomplete dominance