一道SAT语法improving sentences的题

题目

一道SAT语法improving sentences的题
Remarkable breakthroughs in gene research may lead to dramatic changes in medical (treatment,where it may be possible to create drugs tailored to a patient's genetic makeup.)
(A)~
(B)treatment,in which they can possibly create
(C)treatment by making it possible to creat
(D)treatment that makes it possible to create
(E)treatment taht makes possible creating
答案选的C,我选的B.我不知道C中it指代什么成分,而且感觉B没有错误.

答案

你选的B,里面的they才是指代不明啊,前面有出现任何复数人群?C里面的it 是倒装的形式语,就好像it is difficult to do sth一样,只不过一个是形式主语,一个是宾语而已,真要指代的话就是指toxxx那些内容,