Concept:The sex of a child is determined by the sex chromosome contributed by the father’s sperm.
Explanation:A mother contributes an X chromosome through her egg, as her chromosome pair is
XX.
A father contributes either an X or a Y chromosome through his sperm, as his chromosome pair is
XY.
If a sperm carrying the father’s X chromosome fertilises the egg, the child receives
XX and develops as a girl.
If a sperm carrying the father’s Y chromosome fertilises the egg, the child receives
XY and develops as a boy.
In this family, all eight children are girls.
Therefore, in every fertilisation, the father’s sperm must have carried his X chromosome.
This means the X component of the man’s sex chromosome was always involved.
Answer:D. The X component of the man’s sex chromosome was always involved.