白勇语法第四章语法第１４练习题，高手帮助

原文：

Although the Superme Court rules as long ago as 1880 that Blacks could not be excluded outright from jury service,nearly a century of case-by-case adjudication has been necessary to develop and enfore the principle that all juries must be drawn from "a fair cross section of the community"

A.原文划线内容

D.is necessary to develop and enforce the principle that all juries must be

我选Ｄ，但题目解释说Ａ现在完成时更符合上下文逻辑关系．原因就是不明白．

请高手帮忙解答一下

沙发

我觉得吧，has been是完成时，说明这个过程已经完成了，其实从a century也可以推断，因为是长时间段，常用完成时

如果选D说明这个过程现在还在进行，而事实上现在黑人的jury service已经获得了（呃，这个应该算常识我想）。所以该过程肯定是已经完成而非现在时态，所以说A更符合逻辑

有道理！

非常感谢