求助：一道语法题目，谢谢

meckychen

1.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
为什么不出助词do？ could have..... than do... 好像不对的。要补的话也应补could啊？
请指点。谢谢。

fylonglong

我也看了很久，有没有可能是这样一种解释：could have是虚拟语气，而后面的particulars of plan do表示现在的情况。