In the above question, I found “proved” as a clue and comma is a support. So to fill the blank i think the best words similar to “proved” is inventiveness or brilliance.
Can anyone please confirm my logic is right or wrong?
You can’t just cherry-pick a word from a phrase (proved) and use it. Instead, you must digest the entire phrase and use its main idea. The main idea of the first clause in this question is tough to get, but it means that he’s proving something obvious. What would be obvious is that someone old writes with maturity.