you may ask why, well its because the fur color is debated weather the fur color will be recessive or dominate, its not up the nature and environment. Lets say the mouse got a recessive fur color from its mom(white fur) and a dominate fur color from its dad (brown), the offspring will obviously get the dominate trait and get brown fur. So that is why it would be B. I am a A student in science, so i know what i'm talking about when it comes to science.