Women have sex chromosomes of XX, and men have sex chromosomes of XY.

Which of a women's grandparents could not be the source of any of the genes on either of her X-chromosomes?

A. Mother's Father.

B. Father's Mother.

C. Mother's Mother.

D. Father's Father.

The father's father contributes only the Y chromosome to his sons, and subsequently to his grandsons.

E. Mother's Mother and Mother's Father.