885 section 11 Q6

6.     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（D）

(E) a significance even greater for the economy than have

请问被补出的为什么是Do而不是Have？

谢谢