During the nineteenth century Emily Eden and Fanny Parks journeyed throughout India, sketching and keeping journals forming the basis of news reports about the princely states where they had visited.

(A) forming the basis of news reports about the princely states where they had
(B) that were forming the basis of news reports about the princely states
(C) to form the basis of news reports about the princely states which they have
(D) which had formed the basis of news reports about the princely states where they had
(E) that formed the basis of news reports about the princely states they

OA : E

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In option E pricely states they had visited is clearly refering to Emily Eden and Fanny Parks

During the nineteenth century Emily Eden and Fanny Parks journeyed throughout India, sketching and keeping journals forming the basis of news reports about the princely states where they had visited.

(A) forming the basis of news reports about the princely states where they had
(B) that were forming the basis of news reports about the princely states
(C) to form the basis of news reports about the princely states which they have
(D) which had formed the basis of news reports about the princely states where they had
(E) that formed the basis of news reports about the princely states they

E is the answer

Which is not placed correctly in C and D.
A and B "forming the basis of news reports" sounds awkward, I guess this is idiom error. If someone can point the exact error it would be great.

During the nineteenth century Emily Eden and Fanny Parks journeyed throughout India, sketching and keeping journals forming the basis of news reports about the princely states where they had visited.

Note: the independent clause in this sentence is "Emily Eden and Fanny Parks journeyed throughout India"
The sentence after the independent clause acts as a modifier (in this case- a participle phrase) and the modifier type is Adverbial modifier.

(A) forming the basis of news reports about the princely states where they had(a verb in the participle phrase make the phrase into a clause. 2 independent clauses cannot be separated by a comma. It is called run on error)
(B) that were forming the basis of news reports about the princely states (run on error)
(C) to form the basis of news reports about the princely states which they have (run on error)
(D) which had formed the basis of news reports about the princely states where they had (run on error. 'had' in the first instance is not required at all)
(E) that formed the basis of news reports about the princely states they ( correct!)

A,C and D can be eliminated due to wrong tense.The context is in nineteenth century , so a past tense should be used.Past perfect ( had visited ) and present perfect ( have visited ) are wrong here.'that were forming' sounds wrong in B.