In 1713, Alexander Pope began
his translation of the Illiad, 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 Illiad, a work that, taking him seven years until completion, and that literary critic Samuel Johnson, Pope’s contemporary, pronounced- why we are using "taking".
B. his translation of the Illiad, a work that took him seven years to complete and that literary critic Samuel Johnson, Pope’s contemporary, pronounced- Better than A. Parallel phrases as well. Please note- He started from 1731 and then took 7 years to complete (we can't say he had been taken, because earlier action is "began")
C. his translation of the Illiad, a work that had taken seven years to complete and that literary critic Samuel Johnson, Pope’s contemporary, pronounced it is-> Verb tense error and Pronoun "it" error
D. translating the Illiad, a work that took seven years until completion and that literary critic Samuel Johnson, Pope’s contemporary, pronounced it as-> Pronoun "it" error
E. translating the Illiad, a work that had taken seven years to complete and literary critic Samuel Johnson, Pope’s contemporary, pronounced it-> Pronoun "it" error
So, I think B.