Hi,
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.
Let us begin the analysis by understanding the meaning of the sentence.
The sentence means that The Treasury Department released the tax plan. This tax plan has a few particulars and a few guidelines. The guidelines of this plan could have been more significant for the economy than the particulars of the plan.
Based on this understanding let us now evaluate the errors in the sentence.
The two entities compared here are "the guiding principles of the tax plan" = X and "the particulars of the plan" = Y. The way the sentence is written, it says that X could have greater significance for the economy than Y. Now here the comparison is ambiguous because it can mean two things:
a. X is more significant for economy than it is for Y.
b. X is more significant for economy than Y is.
Since the logical comparison should be between the guidelines and the particulars of the tax plan, the sentence does not present proper comparison. It has the meaning error.
Let us now run the process of elimination:
Choice A: Meaning error as discussed.
Choice B:
a. The same meaning error as A.
b. "a significance that is even greater" is wordier than "even a greater significance"
Choice C: When it comes to repeating the verb, it is unidiomatic to place "has/have/had before the subject when they are used as the main verb. However, helping verb can be written before the subject when used in place of complete verb. Let's take an example here:
Mary has sung more songs in school concerts than Amy has sung. Correct.
Mary has sung more songs in school concerts than Amy has (sung). Correct.
Mary has sung mores songs in school concerts than has (sung) Amy. Correct.
Now let's take another set of examples:
Amy has more pencils than Mary has. Correct.
Amy has more pencils than Mary does. Correct.
Amy has more pencils than does Mary. Correct.
Amy has more pencils than has Mary. Incorrect
Since this choice follows the same construction, use of "have" before "the particulars of the plan" is incorrect
Choice D: Correct answer. "Do" or "does" can be used after and before the subject.
Mary has more pencils than does Amy. Correct.
Choice E:
a. Wordy expression as B.
b. Verb error as C.
I hope now the difference between choices C and D is clear. Also, if you could provide the source of this question, we could ascertain the quality of the question.
Thanks.
Shraddha
(edited a typographical error in this post)