第25题: [单项选择]It is thus of exceptional importance ______ extinction theories, but until now problems with dating have limited its potential. A. for a testing purpose on B. as a testing reason in C. as a testing ground for D. for some useful ends of 参考答案:C 答案解析:[注释]结构上需要as 来引导,[B] 的搭配不对,所以[C] 为正确答案。