Конечно, давайте переделаем данные утвердительные предложения в отрицательные:
1) I often play with my little sister.
- I do not often play with my little sister.
2) We like big dogs.
3) You do your homework every day.
- You do not do your homework every day.
4) Sometimes they go to the cinema.
- Sometimes they do not go to the cinema.
5) Rex lives in a doghouse.
- Rex does not live in a doghouse.
6) He plays the piano very well.
- He does not play the piano very well.
7) He is drinking milk now.
- He is not drinking milk now.
8) You are wearing jeans today.
- You are not wearing jeans today.
9) I am watching TV at the moment.
- I am not watching TV at the moment.
Эти преобразования помогают изменить утвердительные предложения в отрицательные, используя соответствующие вспомогательные глаголы ("do/does", "are", "is") с отрицанием "not".