Scholars have little doubt whether the latter years of Egypt's Old Kingdom were marked by economic decline and a breakdown in the centralized system of government, disasters likely brought about by changes in the flow of the Nile.
A) whether the latter years of Egypt's Old Kingdom were marked
B) as to whether the latter years of Egypt's Old Kingdom were marked
C) that the latter years of Egypt's Old Kingdom were marked
D) about the latter years of Egypt's Old Kingdom having been marked
E) about whether the latter years of Egypt's Old Kingdom was marked
This question is based on Idiomatic Usage and Construction.
The conjunction ‘whether’ is generally used to convey an indirect question involving stated or implied alternatives. This sentence does not convey any alternatives. The underlined portion merely states what scholars have little about. The structure of the sentence is such that the noun ‘doubt’ should be followed by a clause. So, Options A and B can be eliminated.
Option E also contains the redundant conjunction ‘whether’. This option also has a subject-verb disagreement. The singular verb ‘was’ does not agree with the plural subject ‘years’. So, Option E can also be eliminated.
Option D is more wordy and less clear. So, Option D can be eliminated.
In Option C, the clause beginning with the relative pronoun ‘that’ is the best construction to be placed after the noun ‘doubt’. This option is absolutely clear. Therefore, C is the most appropriate option.