Ответ:

  1. I have got a cap.
  2. I have got a yellow cap.
  3. I am an actor.
  4. I am a famous actor.
  5. Is he an actor?
  6. Is he a Russian actor?
  7. Is he an English actor?
  8. She is not an actress.
  9. They are — actresses.
  10. I am a diplomat. They are — diplomats too.
  11. I am an economist. He is not an economist. He is a banker.
  12. She is not a dentist. She is a vet.
  13. Are they — engineers?
  14. — Galya has got a kitten. The kitten is red.
  15. — Vitya has got a bike. The bike is fast.
  16. — Valya has got an apple. The apple is red.
  17. — Tanya has got a helmet. The helmet is blue.
  18. — Varya has got an orange. The orange is big.
  19. — Danya has got a camera. The camera is in the bag.
  20. — Olya has got a puppy. The puppy is funny.

Правило: артикль a/an употребляется с одним исчисляемым предметом, an — перед гласным звуком; the — когда предмет уже упоминался; перед существительными во множественном числе и именами людей артикль обычно не ставится.