The allele for polydactyly is dominant,but most individuals do not exhibit the polydactyly trait.Which of the following explains why this occurs in nature?

A) The allele for polydactyly is completely penetrant
B) The allele for polydactyly is never expressed
C) The allele for polydactyly is incompletely penetrant
D) The allele for polydactyly is variably expressive
E) None of these is an adequate explanantion