Answer:
d.fathers father
Explanation:
A woman obtains one chromosome from her mother and one from her father. Her mother obtained one chromosome from her mother and one from her father so both the maternal grandparents could be source of the genes found on woman's X chromosome.
Woman's father has only one X chromosome which he definitely inherited from his mother. His father or woman's paternal grandfather contributed Y chromosome to his son and hence he could not be responsible for any of the genes on woman's X chromosome.
