语法真题一道 平行结构的类型

以下是引用寂寞的自由在2003-12-25 5:29:00的发言：
1. !!! Temporary-employment agencies benefit not only from the increasing demand for clerical workers but also the higher profits made when highly paid professionals are placed, requests for whom have increased in the recent wave of corporate takeovers.   C--àE
(A) the higher profits made when highly paid professionals are placed, requests for whom
(B) the higher profits that are made in the placement of highly paid professionals, requests for whom
(C) from the requests for highly paid professionals, who make higher profits for the agencies when placed and whose requests
(D) from highly paid professionals, whose placement makes higher profits for the agencies and whose requests
(E) from the higher profits made in placing highly paid professionals, requests for whom

正确答案是E，可是C错在哪里呢？C的the request for 和原句中的那个DEMAND不是很好的平行对照吗？搞不明白，谢谢大家的帮助