What's she doing at the grocery store?
She's buying.
What's he doing at the movie theater?
He's watching.
What's he doing at the department store?
He's shopping.
What's she doing at the library?
She's borrowing.
What are they doing at the library?
They're borrowing.
What are they doing at the movie theater?
They're watching.
What's he doing at the post office?
He's mailing.
What's he doing at the park?
He's kicking.