33. Those products are friendly to the environment.

be friendly to the environment = environmentally-friendly

34. We are responsible for preventing environmental pollution.

Doing smt be one's responsibility = be responsible for doing smt

35. I think we should put a lot of trash cans around the schoolyard.

suggest doing smt = I think S should do smt
36. We should exercise a lot so that we can have a healthy lifestyle.

To V + O , clause ( S + V ) = clause ( S + V ) so that S can/could V + O

37. Polluted air can cause illnesses and even death.

Pollute -> polluted ( adj ) để bổ nghĩa cho " air "

38. Mr. Thomas is one of the most famous environmentalists in the world.

Cấu trúc: be one of the + tính từ ở dạng so sánh hơn nhất + N ( số nhiều )

39. Using less energy helps us save money and conserve the environment.

40. Solar energy can be easily used in tropical countries.