The revision that would best improve the parallel structure in sentence 18 from paragraph 6 is:
D. By creating unrealistic expectations, decreasing attention spans, and skewing worldviews, social media is shaping a generation that struggles to understand the complexities of the real world.
This option maintains a consistent structure by using gerunds ("creating," "decreasing," and "skewing") for all three phrases, thus enhancing the parallelism in the sentence.