Consider the following statements. (a) Mendel selected 16 different varieties of the pea and grouped them into eight pairs. (b) The gene responsible for the condition known as sickle-cell anemia demonstrates multiple allele inheritance. (c) When both parents are homozygous for a recessive trait, they run a one-in-four chance that the recessive trait will be expressed in their children. (d) The genotype of the F1 generation is heterozygous. Which of the above statements is/are correct?