IMO B.

Analysis: The issue here is about parallelism .

Although the rare books were initially housed ......, they had moved to a museum .... when the library shelves became crowded with new literature and periodicals

A ,C and D fail addressing this problem .

E Says ..."they were moved a decade ago to the museum.", which is wrong .

Hence IMO : B

IMO : B

IMO B

Imo b

They moved looks like books themselves moved to a museum which definitely doesn't make sense. Hence like above they(books) were moved (By someone) to the museum.
But E...fails parallelism HOUSED....................., THEY WERE MOVED.
since the structure doesnt seem to be parallel. we eliminate E.

Hence B stands by POE as well

vatsalroxy wrote:They moved looks like books themselves moved to a museum which definitely doesn't make sense. Hence like above they(books) were moved (By someone) to the museum.
But E...fails parallelism HOUSED....................., THEY WERE MOVED.
since the structure doesnt seem to be parallel. we eliminate E.

Hence B stands by POE as well

Indeed OA is B.

I completely missed "Although X , Y" idiom/construction where X and Y must be parallel.

This question has two main error issues - Verb choice (based on parallelism) and adjective placement.

The verbs "housed" and "moved" have to be parallel (including their helping verbs)

A. is incorrect becuase "were ... housed" is not parallel with "had moved"
B. the verbs are parallel
C. "were housed" is not parallel with "moving"
D. "were housed" is not parallel to "moved"
E. "housed" is not parallel to "were moved"

Thus the issue of parallel eliminates all but B.

another issue of the correct placement of initially is also in play. you have to ask to what is the adverb referring and here initially is referring to when they were housed - thus the best placement is directly before the verb "housed" E is certainly wrong becuase initally is then referring to "a century ago" which is confusing.