Answer the following question given this paragraph: 

One of the exciting things about expecting a child is wondering if the baby will be a boy or a girl. There are many superstitions about how one might influence or predict the outcome. But what really determines if a baby is male or female? We now know that the gender of a baby is determined by a special pair of chromosomes known as the sex chromosomes.


Q: The gender of a baby is determined by what special pair of chromosomes?


A:
sex chromosomes