The answer is cotton. It is natural because it is grown and easily woven in to clothes :)
Thyriod gland is the right answer
We suppose the black fur is A and the white fur is a. The capital letter represents the dominant. Then the heterozygous black male is Aa and homozygous white female is aa. Then the offspring has two types, Aa and aa. The possibility of these two is equal and both are 50%.
