Answer:
The correct answer is option B. "25%".
Step-by-step explanation:
According to Mendel's laws of Inheritance, the genotype of the offspring from a cross between chickens where the mother has the genotype Aa and the father has the genotype Aa will be 25% AA, 50% Aa and 25% aa. Since the allele for a single comb is recessive, only chickens with a aa genotype will develop a single comb. Therefore, the percent chance that the offspring will have a single comb is equal to 25%.