— The MP3 cost me about 2,000 yuan. 

— Well, it was crazy of you to spend so much money _____ you could buy a cheaper one. [ ]

A. when

B. unless

C. if

D. because

环境在自然力作用下消纳污染和产生出自然资源的总过程称为（）

A.物质生产

B.自然净化

C.环境生产

D.资源再生