39.
(A) how many greenhouse gases there are
(B) how long greenhouses have been used
(C) what a greenhouse is and how it works
(D) what greenhouse gases are and where they come from
答案:登入後查看
統計: A(28), B(45), C(237), D(67), E(0) #2716778
統計: A(28), B(45), C(237), D(67), E(0) #2716778