The short lived Corsican Republic was a uniquely progressive nation
at its 1755 founding for deciding to grant full voting rights to all adult citizens.
(A) at its 1755 founding for deciding to grant
This choice incorrectly says that the country was uniquely progressive <<at its 1755 founding>> which is absurd in meaning.
(B) for the decision at its 1755 founding to grant
This choice has no evident errors. Hence, this choice is likely the
CORRECT answer.
(C) when it was founded in 1755 for its decision to grant
This choice incorrectly implies that the country was founded in order to grant full voting rights to all adult citizens.
(D) by deciding at its founding in 1755 on the granting of
<<at its founding in 1755>> is an awkward and wordy construction that is not typically seen in a correct GMAT SC choice.
(E) in deciding at its founding in 1755 to grant
In this choice<< in deciding at its founding in 1755 to grant>> is wordy and such a choice is not typically seen in a correct GMAT SC answer.
Answer:
Option B