d. "not morose, misanthropic, and revengeful, but cheerful, hopeful, and forgiving."
Parallel structure is using the same grammatical structure for elements in a list. This helps with the flow of the sentence and ideas, as well as aids the reader in seeing how the items are similar or different. In this case, the items in both lists are written as adjectives. This allows the reader to see the similarities among the that are grouped together and how the contrast to each other across the conjunction "but". The phrase "two hundred and fifty years" is not part of parallel structure in this sentence.
