In chickens, comb shape is determined by two independent genes (r and p). a walnut comb is produced when at least one dominant allele r is present at one gene locus and at least one dominant allele p is present at a second gene locus (genotype r_ a rose comb is produced when at least one dominant allele is present at the first locus and two recessive alleles are present at the second locus (genotype r_ pp). a pea comb is produced when two recessive alleles are present at the first locus and at least one dominant allele is present at the second (genotype rr if two recessive alleles are present at the first and the second locus (rr pp), a single comb is produced. give genotypes for comb shape of the parents in the following cross: rose crossed with pea produces 2 walnut, 1 single, and 1 pea offspring. a) rr pp × rr ppb) rr pp × rr ppc) rr pp × rr ppd) rr pp × rr ppe) rr pp × rr pp