生态安全有两类（）。
A.辐射安全与植被安全
B.水安全与空气安全
C.土壤安全和阳光安全
D.要素安全和功能安全
参考答案：D
—Look, Victor. This brown cat is ________ than that white one.
—Yes. And it is _____ of all these cats.
A．big; big
B．bigger; bigger
C．bigger; big
D．bigger; the biggest
How about _____ the music? [ ]
A. listen to
B. listen
C. listening to
D. listening
