What makes a girl a girl...

Sophie: Mama, you know how girls can drive straight with their knees, and no hands?

Me: Yeah....

Sophie: Can boys do that?

Me: Yes. Girls and boys can pretty much do all the same things.

Sophie: Except girls are tougher than boys.

Me: Yes. Yes they are. 

Sophie: There are just three things that make girls and boys different.

Me: Oh yeah, what are they?

Sophie: One, girls are tougher than boys. Second, their privates are different. And third, one is a girl and the other is a boy. See, three things.

Me: Yes, exactly right.