请教

请教下题为什么选E？it指代什么？

Dental caries and gingivitis can be exacerbated not only by the foods patients eat but also by when the patients eat them.

(A) not only by the foods patients eat but also by when the patients eat them

(B) by not only the foods patients eat but also by when the patients eat them

(C) not only by the foods patients eat but also by time when the foods are eaten

(D) by not only the foods that are eaten by patients but also by the times the foods are eaten

(E) not only by what patients eat but also by when they eat it

flora mm,

强烈推荐先参考GMAT区域各版块的置顶贴，好东东多多！

先请下载目前市面上最全的GMAT语法复习材料 － 俗称“大全”：
http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=21000&page=1

关于如何与你手中的资料题号对应，请参考：
http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=24247&page=1

若对大全中各题目有任何疑问，可以先参考前辈们的精彩讨论，置顶贴中有如下汇总：

OG提问总结
http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=27472&page=1

885提问总结
http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=27532&page=1

补充题250题
http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=27505&page=1

最新真题22题
http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=59129&page=1

GWD讨论汇总
http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=56794&page=1

备注：GWD不含在“大全”中，完全不懂什么是GWD的可以参考：
http://forum.chasedream.com/dispbbs.asp?boardID=34&ID=58504&page=1

如果前辈们的讨论仍未能解决你的问题，请把原题目顶出来，继续讨论。

若有新题问题，请按照标准方式发帖，即方便大家回复，又方便后人查阅参考。
http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=36320&page=1

谢谢！

祝你复习过程顺利、愉快！国庆节快乐！