Sentence Correction

The guiding principles of the tax plan released by the Treasury Department could have even a greater significance for the economy than the particulars of the plan.

(A) even a greater significance for the economy than
(B) a significance that is even greater for the economy than
(C) even greater significance for the economy than have
(D) even greater significance for the economy than do
(E) a significance even greater for the economy than have

OA: D

Please explain why B is wrong

B is missing parallelism.

Out of C and E, E looks better and I cannot figure out why OA is D and why E is wrong

I was confused between C and D.
And initially picked "C", but after looking at OA, realized have is the regular verb and not aux. so it can be replaced by "do".
This is because we generally use "do" to replace regular verbs in parallel clauses.

Correct me if I am wrong here.

confused between "c" and "d"