Hi j_shreyans,

Good work in eliminating answer choices A, B and C (all incorrectly use the singular "is" rather than the plural "are" as you no doubt spotted). Choosing between answers D and E has to do with the preposition rule that says a preposition should be as close as possible to the noun that it's modifying. For example:

Here is the glass I put the ice in. <--- INCORRECT

Here is the glass in which I put the ice. <--- CORRECT (the noun "glass" and the preposition "in" are close together; the pronoun "which" takes the place of the noun "glass," so "in which" means "in the glass")

Use the above preposition rule to eliminate answer D in favour of answer E.

(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 <--- CORRECT

The pronoun "which" takes the place of the noun, "collateral," so "against which" means "against the collateral." Answer E is correct because it places the preposition "against" closer to the noun "collateral."

j_shreyans wrote: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

A which-clause set off by commas serves as a NON-ESSENTIAL modifier.
A non-essential modifier can be removed without changing the core meaning of the sentence.
If we omit the which-clause in A, B and C, we get:
Declining VALUES for farm equipment and land IS going to force many lenders to tighten or deny credit.
Here, is (singular) does not agree with values (plural).
Eliminate A, B and C.

In D, use as collateral is redundant with to borrow against: to use X as collateral MEANS to borrow against X.
Eliminate D.

The correct answer is E.