Verb Tense SC-Oxford dictionary

[rishisbook]

In 1860, the Philological Society launched its effort to create a dictionary more comprehensive than the world had ever seen; although the project would take more than 60 years to complete, the Oxford English Dictionary had been born.
would take more than 60 years to complete, the Oxford English Dictionary had been
took more than 60 years to complete, the Oxford English Dictionary was
would take more than 60 years to complete, the Oxford English Dictionary was being
would take more than 60 years to complete, the Oxford English Dictionary was
took more than 60 years to complete, the Oxford English Dictionary was about to be

Correct Answer D. How can D be the answer?I selected B as the answer since it makes use of two simple past tenses 'took' and 'was' to show that both things happened at the same time in the past.

RON, can you please explain this particular sentence?

[jnelson0612]

Check out Stacey's explanation as to why B is incorrect: in-1860-the-philological-society-launched-its-effort-t421.html