Re: Work with facts
People have two legs.
There are very small number of cases when someone can be born with one leg only, or without any, but we call it a “medical condition“ and it does not change our assumption they people are born with 2 legs unless someone does not.
Same with chromosomes. We either have XX or XY. Unless someone is born with a medical condition. And unlike number of legs that we can reduce we can’t change our chromosomes.