A fruit fly with a gray body (b) and red eyes (R) mates with a fruit fly with a brown body (B) and white eyes (r). The offspring all have brown bodies and red eyes. However, when the offspring
mate with each other, they produce some flies with gray bodies and white eyes and some with brown bodies and red eyes. They also produce offspring that resemble the original pair of flies.
Why does the third generation of flies have combinations of traits that were not seen in the first generation?

A. The alleles for the traits are recessive.
B. The alleles for the traits assort independently.
C. The alleles for the traits are dominant.
D. The alleles for the traits segregate into gametes.