[求助]GWD17-31没有讨论过的题目

31. GWD17-Q31:

The agreement, the first to formally require industrialized countries to cut emissions of gases linked to global warming, is a formal protocol by which 38 industrialized countries must reduce emissions of these gases by 2012 or face heavy penalties.

A.      by which

B.       for which

C.      under which

D.      such that

E.       wherein

这道题不理解，应该怎么选择呢？自己胡乱选的a,但是正确答案是c，nn帮忙分析一下好么？

I think c is correct

a: by which means 通过它（指代协议），工业国家必须怎么着

b：for with means 为了它，语义不合理

c under which means 在这项协议下，工业国家必须怎么着

语义上来说c明显比a合理

明白了，谢谢阿