Thanks for the question! (B) is incorrect here because the passage doesn’t subject anything to a “political test case.” No lines support that; test cases are supposed to test an idea to see if it holds in certain situations or not (an example would be an edge case in programming if you’re familiar, but also, when you check to see if your program works, you feed it samples which are test cases). Nothing like that happens in the passage, so (B) is wrong.
Hope this helps! Feel free to ask any other questions that you might have.
