This question is testing MODIFIERS, SUBORDINATE CLAUSES, and PARALLELISM.

In 1713, Alexander Pope began his translation of the Iliad, a work that, taking him seven years until completion, and that literary critic Samuel Johnson, Pope's contemporary, pronounced the greatest translation in any language.

A. his translation of the Iliad, a work that, taking him seven years until completion, and that literary critic Samuel Johnson, Pope's contemporary, pronounced
- "a work" is correctly modifying "his translation of the Iliad." A noun modifier is allowed to "hop" over a short essential modifier (usually a prepositional phrase) to modify the noun preceding it. So it's understood here that his translation is the work in question, and not the original Iliad.
- Here, we have the construction "a work that, [modifier], and that..." There is no completion to the subordinate clause beginning after the first "that." We could say instead "that took seven years... and that SJ pronounced..."

B. his translation of the Iliad, a work that took him seven years to complete and that literary critic Samuel Johnson, Pope's contemporary, pronounced
- "a work" is correctly modifying "his translation of the Iliad." - see above
- The construction "a work that ____ and that ___" is parallel. Correct.


C. his translation of the Iliad, a work that had taken seven years to complete and that literary critic Samuel Johnson, Pope's contemporary, pronounced it as
- Verb tense awkwardness. If we say "he began a work," we don't want to modify it with "a work that had taken." The PAST PERFECT tense should describe events that happened before a past tense event, not after.
- Subordinate clause issues. "... and that SJ... pronounced it..." In this subordinate clause, "SJ" is the subject, "pronounced" is the verb, and "that" (referring to "work") is the object. Since we already have an object, the "it" is redundant.

D. translating the Iliad, a work that took seven years until completion and that literary critic Samuel Johnson, Pope's contemporary, pronounced it as
- an APPOSITIVE such as "a work" can only modify a NOUN. If we switch "his translation" to "translating," this is no longer a noun. The only noun there is "the Iliad," so the rest of the modifying phrase is now describing the ancient text, and not Pope's 1713 translation. This meaning doesn't work.
- same "it" issue as in C.

E. translating the Iliad, a work that had taken seven years to complete and literary critic Samuel Johnson, Pope's contemporary, pronounced it
- same issue with "translating"
- by removing "that," the clause "SJ pronounced it..." is now an independent clause, not properly joined to rest of the sentence. We want that clause to modify the work, not act as a stand-alone sentence.

Hope this helps!