To determine which detail best supports the answer to Part A, we would need to understand what Part A's answer is. However, the answer likely pertains to themes of fear, prejudice, and persecution similar to the Salem trials, especially given that we are considering events in U.S. history that resonate with the Salem witch trials.
With that context in mind, Option A ("In the United States, groundless fears, prejudices and demagoguery produced three notable events that echoed the Salem trials.") establishes a clear connection to the theme of the influence of fear and prejudice in American history, directly referencing the Salem trials.
Option B discusses the internment of Japanese Americans during World War II, which also relates to fear and prejudice. While it is significant, it is not as overarching as the argument made in Option A.
Options C and D relate to McCarthyism, which is indeed an example of fear and accusations leading to persecution, but they are more focused on specific actions rather than anchoring the broader thematic connection to the Salem trials.
Given this analysis, the best supporting detail is:
A. "In the United States, groundless fears, prejudices and demagoguery produced three notable events that echoed the Salem trials." (Paragraph 19)