Wrong trigger. The premises tell us that MacArthur either did know or should have known his actions would hurt others, leaving open the possibility he didn’t know. As such, we can’t activate this conditional statement.

(B) leads to the wrong conclusion. We aren’t concerned with whether others should have followed MacArthur’s diet Advice. We only care whether MacArthur should have published the book in the first place.

Leads to the wrong conclusion. If the sufficient and necessary conditions were swapped, this would support our conclusion; (C), however, only lets us prove a book should be covered, not that it shouldn’t.

Wrong trigger. We know that MacArthur’s book did succeed in its goal of helping people lose weight, so we can’t use this conditional statement.

MacArthur either did or should have known his book would hurt people. (E) tells us that, if that is the case, he shouldn’t have published his book. As such, (E) allows our conclusion to be properly drawn.