Dogs have a wide range of coat colors, even within a given breed of dog. Scientists studying animal genetics ran studies by mating two dogs with a solid brown coat. The resulting offspring had light brown, dark brown, black, and spotted coats. After studying several mating cycles, scientists concluded that while brown coats are more common, there does not appear to be a fixed ratio of phenotypes. What is the most likely explanation for the inheritance pattern of dog coat color?

Dog coat color is a polygenic trait.
Dog coat color is controlled by a pleiotropic gene.
Dog coat color is controlled by epistasis inheritance.
Dog coat color follows an incomplete dominance pattern of inheritance.