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_ P_). 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 P_). 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 PP
b) Rr pp × rr Pp
c) Rr pp × rr PP
d) RR pp × rr Pp
e) Rr pp × Rr Pp

Option B, Rr pp × rr Pp

Explanation:

Given

Walnut Comb is produces when  one dominant allele R is present at one gene locus and at least one dominant allele P is present at a second gene locus - R* P*

Rose Comb - at least one dominant allele is present at the first locus and two recessive alleles are present at the second locus - R* pp

Pea comb - two recessive alleles are present at the first locus and at least one dominant allele is present at the second  - rr P*

Single comb - two recessive alleles are present at the first and the second locus  - rrpp

Parent are rose combed and pea combed

For being rose genotype must be R* pp

and for being pea combed genotype must be rr P*

Rr pp x rr Pp

will  produce

Walnut comb  with genotype Rr Pp

Single comb  with genotype rrpp

and pea comb  with genotype rrPp

Hence, option B is correct

1. b.

2. d.

3. a.

5. d.

6. c.

these are the only ones that i know, i hope this , and good luck.