The author uses the word "immediacy" (line 39) most likely in order to express

I understood the majority of the missing premise questions and now I’m trying to work on the argument completion drills. As I write the conclusion, my answer is basically the contrapositive of the correct answer. I am not sure what I’m doing wrong since there are no explanations. For example: P: X ? Y P: not X ? A P: A ? not B C:     ?       My answer was not Y ? not B But the correct answer is B ? Y I do not understand why?