33. I suggested our should keep environment unpolluted.

34. I think their class should be cleaned.

35. The peach which she ate was still green.

36. Although we had invited her to the party, she didn't come.

33. Why don't we keep our environment unpolluted?

→ I suggest our should keep environment unpolluted

34. I think they should clean their class.

→ I think their class should be cleaned

35. She ate a peach. The peach was still green

→ The peach which she ate was still green

36. We had invited her to the party, but she did not come.

→ Although we had invited her to the party, she didn't come

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