The possible answers are:
1) CWCW
2) CBCB
3) CBCW
4) CWCW or CBCW
The correct answer is 1) CWCW.
As we already know, the two traits and their genes are codominant. This means that if an individual has both of the genes or the CBCW genotype (heterozygous genotype) it will fully express both of the traits. This will mean that the chicken will have both white and black feathers.
Therefore, the only situation in which the chicken will have only white feathers is the one when the chicken has a CWCW genotype, only genes for white feathers ( Cw homozygous genotype).
