What is he doing?
He's playing soccer/football.
What are they doing?
They're studying.
What are they doing?
They're swimming.
What is she doing?
She's running.
What is she doing?
She's reading.
What is he doing?
He's singing. / He's playing the guitar.
What is he doing?
He's watching TV.
What is he doing?
He's driving.
What are they doing?
They're cooking.
What is she doing?
She's eating watermelon.