A and B are wrong because of misplaced modification.
C is a horrible sentence with no semblance of balance of tense form, with the distant past prefect appearing along with a future tense.
D. Hopefully restringing is incongruous. You can’t hope to restrain and also same time have retrained; making more expensive borrowing is jarring.
E is the odd man out and ought to be right; the vexatious -it- can at best be holding a filler value, just as it does so often in normal and formal writing. needing no referent.
E.g: 1. Wanting to thwart Messy from scoring at will, the Spanish coach put three backs around him, making it difficult for him to pierce the cordon.
2. Seeking to prepare hard for the GMAT, Jack bolted to his farm house fifty miles away, making it difficult for his friends to disturb him.
Or am I wrong? I will wait until the OA and OE arrive.