Final answer:
The correct statement is b) The genes A and B assort independently, which means they are either on different chromosomes or far apart on the same chromosome to allow for frequent recombination.
Step-by-step explanation:
When an individual with an AB/ab genotype is testcrossed and four classes of testcross progeny are found in equal frequencies, it indicates that the genes A and B assort independently. This is because the observed equal frequency of the four possible genotypic combinations in progeny corresponds to both parental and non-parental (recombinant) types, suggesting that these genes are not linked, or are located far enough apart on the same chromosome for crossing over to occur frequently.
Therefore, the correct statement is b) The genes A and B assort independently. This means that they are either located on different chromosomes or located so far apart on the same chromosome that recombination occurs at a frequency similar to that of genes on different chromosomes. A Punnett square can be used to predict the outcomes of these genetic crosses, reflecting the principle of independent assortment.