I understand that Option C is the best available option, but I dont quite understand how the parallelism fits.
From what I have learnt "Not X but Y" has a similar usage as that of other parallelism pairs. So the part of the sentence that follows "but" should make sense with what comes before "not" in the same sentence.
For example,
The goal was scored not by Messi but (was scored) by Ronaldo.
In this question if we follow the same thought process, we get the below sentence.
The voluminous personal papers of Thomas Alva Edison reveal that his inventions typically did not spring to life in a flash of inspiration but (did) evolved slowly.
As we can see the 2nd part of the sentence "did evolved slowly" does not quite make sense.
Would be great if anybody can help clear this doubt.
GMATNinja KarishmaB IanStewart