1.He is a great cook.He is/can cook really well.
2.look!Mary is dance/dancing.
3.Are you/Can you ride a bike?
4.Harry and Tom aren't/isn't sleeping.They're in the garden.

Спасибо!!!!!!

1 - can, 2 - dancing, 3 - can, 4 - aren't

1. He is a great cook. He can cook really well.2. Look! Mary is dancing.3. Can you ride a bike?4. Harry and Tom aren't sleeping. They're in the garden.