Which of the following is NOT one of Mendel's hypotheses to explain the results of his P, F1 and F2 crosses?
a. Adult plants carry a pair of genes that will determine the inheritance of each allele.
b. Adult plants always have traits that are governed by a single pair of alleles, but the number of possible alleles varies with each trait.
c. The pairs of alleles separate in the formation of gametes so that each gamete gets one allele of the pair.
d. If an adult plant has two different alleles, one is recessive to the other.
e. If an adult plant has two different alleles, one is dominant over the other.