Are they playing basketball?
Yes, they are.
Are they ice skating?
Yes, they are.
Are they cycling?
Yes, they are.
Are they playing basketball?
No, they aren't.
Are they surfing?
No, they aren't.
??? (No, they aren't)
Are they playing football?
Are they playing chess?
Yes, they are.
??? (Yes, they are.)
Are they sailing?
??? (No, they aren't)
Are they playing table tennis?
??? (Yes, they are)
Are they skipping?