[問題]OG(VR)16

[sweetymanman]

OG(VR)16:
Declining values for farm equipment and land, the collateral against which farmers borrow to get through the harvest season, is going to force many lenders to tighten or deny credit this spring.

(A) the collateral against which farmers borrow to get through the harvest season, is
(B) which farmers use as collateral to borrow against to get through the harvest season, is
(C) the collateral which is borrowed against by farmers to get through the harvest season, is
(D) which farmers use as collateral to borrow against to get through the harvest season, are
(E) the collateral against which farmers borrow to get through the harvest season, are

題目答案是E
我的問題是：但到OG(VR)的針對選項D的解釋是：
use as collateral to borrow against is redundant
不知道可否有人可以解說哪裡redundant？