A woman heterozygous for colourblindness marries a colourblind man. What would be the ratios of carrier daughters, colourblind daughters, normal sons and colourblind sons in the F1-generation?
(a) 1 : 2 : 2 : 1
(b) 2 : 1 : 1 : 2
(c) 1 : 1 : 1 : 1
(d) 1 : 1 : 2 : 2