Is she playing the piano?
Yes, she is
Are they reading a book?
No, they aren't
Is he listening to music?
No, he isn't
Are they cooking?
Yes, they are.
What are they doing?
They are playing tennis
What's he doing?
He's playing the guitar
Is she riding a bike?
No, she isn't
What's he doing?
He's playing football /
He's playing soccer
What's she doing?
She's playing basketball