Answer: B. Riku
Step-by-step explanation:
We see Riku's immediate interest in the article, as well as his tendency to think for himself. His opinion is opposed to that of Maria who seems to argument her point of view based on authority: Frederickson has always been an apologist for Joseph Conrad. To Conrad, Africa is the same thing as savagery. Practically a symbol for it.
Edgar is the one that asked the crucial question, Victor showed interest, but it was only Riku that decided he'd go out of his way in order to find out something new: In that case, I'm going to find an article that agrees with Frederickson. Why don't you and Maria find one that disagrees?