I think the answer is C but that’s just a guess
Parallel Element = 'not morose, misanthropic, and revengeful, but cheerful, hopeful, and forgiving,'
This sentence follows the same gramatical structure of using two words with a comma and then ending the rule of three with an and. These complex entence is also seperated through by rude of the conjuction of but.
I believe the answer is bracket sentence that address your point. i googled it.
hope this helps
