They .... playing basketball.
aren't
He is ..... gymnastic.
doing
What are they doing?
They're playing volleyball.
Cheetahs are good at ....
running
What are they doing?
They're running.
What are they doing?
They're playing tennis.
They ..... swimming.
are
Kangaroos are good at ....
jumping
He's .... a ball.
bouncing
They ..... playing ping-pong.
aren't
Penguins are good at ....
swimming
He is ...... a ball.
catching