新prep1-182

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The organic food industry has organized a successful grassroots campaign—using Web sites, public meetings, and also mass mailings—that have convinced the Department of Agriculture to change the proposed federal regulations for organically grown food.

A. using Web sites, public meetings, and also mass mailings—that have convinced

B. using Web sites, public meetings, and mass mailings—that has convinced

C. by using Web sites, public meetings, and mass mailings—in convincing

D. by the use of Web sites, public meetings, as well as mass mailings—that convinced

E. which used Web sites, public meetings, and mass mailings—in convincing

请教这题为什么要用完成时态？ D为什么不好？ 难道因为as well as不如and好吗？

这道题选B吧

题目原句用的现在完成时，除非句子中有明显的时间标志，否则不要改变原句所用时态

而且by the use of 用法也不对, 动作的发出者The organic food industry ，所以用using

破折号里的插入语用什么都行。但是B和C的后面B 肯定没错。C就不好说，可以用（to convince 替代表目的，也可以向AlienX说的）。记号，回来看。

这道题我错选了C，现在看来如果是C的话完全可以不用破折号，且有改变句意的嫌疑。

但是对破折号的意义还是不太清楚，盼望有NN能帮助