Here are the answers with the correct form of the words given:

29. **Traditionally** the Ao dai was frequently worn by both men and women.
30. Some designers **modernized** the Ao dai by printing lines of poetry on it.
31. Thi Vai River was used for years as a **waste** dump.
32. They are planning to protect the forest from **industrial** development.
33. He is one of the most famous **environmentalists** in the world.
34. It was your **carelessness** to leave matches where children could get them.

For the sentences in section VIII:

35. **Mr. Brown is talking to some volunteers.**
36. **When the trucks are covered with trash, the ground is left.**

Rewriting sentences for section IX:

37. **Jack's mother asked Jack not to forget to do his assignment.**
38. **Nobody is better than Lan in my class.**
39. **Because of their good performance, they won that match.**
40. **My father is good at teaching Math.**