Ответ:
1. We have been waiting for George...
2. Dora has been playing chess since she was 6.
3. they have been listening...
4. Jane has been learning...
5. What has she been doing?
6. It has been snowing...
Объяснение:
Все предложения здесь в Present Perfect Conitnuous: have/has been -ing
Во вором предложении ошибка: так не говорят since 6 years - since she was six. И в пятом не может быть дважды "do"