1.Kate is not riding a on a sledge.
She is skating.
2.Nick and John aren't throwing snowballs.
They are riding on a sledge.
3.Alex isn't making a snowman.
He is skating.
4.Stacy and Andy aren't skating.
They are making a snowman.
5.Mike is not playing hockey.
He is making a snowman.
6.Kate and Alex are not making a snowman.
They are skating.