If You Were to Breed a Black Male Guinea Pig

If you were to breed a black male guinea pig to a brown female guinea pig in an attempt to determine which one was homozygous dominant and which one was homozygous recessive,how could you be certain that the guinea pigs are truly homozygous?

A) The guinea pigs would be homozygous for black (or brown) coat color if each strain could be bred for many generations and only black (or brown) colored offspring were produced.
B) If the immediate parents of the black (or brown) guinea pigs were both of that color, it proves they are homozygous.
C) If a cross between the black and brown guinea pig produced four all black offspring, the black guinea pig would have to be homozygous for black coat color.
D) If a cross between the black and brown guinea pig produced four all black offspring, this would prove the black guinea pig was recessive.
E) Only microscopic examination of the guinea pig's genes could absolutely confirm homozygosity.