Trees can keepcool.
A. usB. weC. our
We need more trees.
A. plantB. to plantC. planting
听音，选出你所听到的单词。
（）（1）A . cleanB. cool C. keep D. car
（）（2）A . hot B. hotter C. get D. getting
（）（3）A .buildingB. changing C. singing D. interesting
（）（4）A .plant B. down C. becomeD. long
（）（5）A .spring B. air C. freshD. rice
Planting treesgood for us.
A. am B. isC. are
Trees can keep the air.
A. clean B. beautiful C. hot