土壤环境质量二级标准是为保障农业生产，（）的土壤临界值。

A.保障工业生产

B.维护人体健康

C.维持自然背景

D.保障农林业生产和植物正常生长

We have ______ some organizations to help the poor students in the western areas of China. [ ]

A. taken up

B. put up

C. picked up

D. set up