请教OG 140

ygjm

    140. 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

答案是E， 请问这里的which 指的是哪个？ borrow against是个固定搭配吗？ 又如何个用法？
谢谢！

braveMBA

collateral--担保物

SnowyDay

brave GG 我找你！