It surrounds the spinal cord is anwser
The genotypes would be 50% Bb and 50% bb
The phenotypes would be 50% brown and 50% white. Hope this helps :)
The second one hope that helps
I think it's option four because as far as I know, red/green color blindness is an example of a recessive, sex-linked trait (encoded on the X chromosome), which results in much more men to suffer from it than women.
Hope that helps!