Answer: Forgive me if I’m wrong, but I think it’s B.
Explanation: The other listed methods draw on existing research, and history. Current theories are unlikely to change simply by reviewing already discovered information. Option B provides new insight and a deeper look, which is more likely to uncover new information.
However, discussion promotes questioning and looking “between the lines” of research/data, and maybe rarely, something new, but also pretty marginal, might appear.
