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