Final answer:
Given that all parent rabbits have very long legs and at least one white fur parent, 100% of the offspring will have very long legs. As for fur color, at least 50% of the offspring will have white fur, given the potential genotypes of the brown parent. Then, the percentage of offspring expected to have both very long legs and white fur is 50%.
Step-by-step explanation:
The question involves crossing rabbits with different leg lengths and fur colors to determine the percent of offspring that will have very long legs and white fur. To solve this, we must understand that leg length and fur color are determined by different genes that segregate independently because they are on different chromosomes. The given information indicates that cc genotype results in very long legs and the cc genotype results in white fur. Since all the parent rabbits have very long legs (and thus must have at least one c allele), and one parent rabbit has brown fur (b genotype unspecified, but must have at least one b allele) and the other parent has white fur (cc), we need to determine the probability that the offspring will inherit a c allele from both parents for leg length, and the c allele from the white parent and a c allele (which must be contributed by the brown parent for them to be white), for fur color.
Without the exact genotype of the brown parent, the best we can deduce is that all offspring will have very long legs (since both parents will provide at least one c allele) and at least 50% will be expected to have white fur (since the white parent provides a c allele and if the brown parent is heterozygous, Bc, they can provide a c allele 50% of the time).
Therefore, the percentage of offspring expected to have very long legs and white fur is 50% (Option B).