GMAT Sentence Correction (SC) | Re: In 1860, the Philological Society launched its effort to

Personally I see no problem in using the B option, it's gamatically correct. The use of "took more than 60 years to complete" emphasises the fact that it took a long time ti finish, but eventually it was done.

HOWEVER that is not the intended meaning of the original sentence. The original meaning is to transmit the idea that the project will take a lot of time to complete, but even so, dispite all future challanges, it has been started.

So there is this slim change of meaning here.
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