What is she doing? She's ...
reading / reading books
What are they doing? They're ...
writing
I'm ...
singing
What are they doing?
They're dancing.
What are you doing?
reading / reading books
What are you doing?
I'm listening to music
What is he doing?
He's playing football / soccer
What are you doing? I'm ...
dancing
What are you doing? I'm ...
writing / writing a letter