Answer: Option A
The sex of a baby is determined by two sex chromosomes inherited from both the genetic parents. A baby will normally inherit one sex chromosome from the mother and one from the father. A woman has two X chromosomes and thus gives either of her X chromosomes. The father has one X chromosome and one Y chromosome, can give either his X or Y chromosome. The egg (from the mother) already contains an X chromosome. Therefore the sex of a baby is determined by the X or Y chromosome of the sperm cell from the father.