In poultry, the genotype–phenotype relationships forcomb shape are R/– P/–, walnut; R/– p/p, rose, r/r P/–, pea;and r/r p/p, single. What will be the comb characters ofthe offspring of the following crosses?
a. A walnut crossed with a single
b. A rose crossed with a walnut
c. A rose crossed with a pea
d. A walnut crossed with a walnut