PT 5 Section 3 RC Q 19

[youminm]

Hello,
I'm having a hard time understanding this question. Could anyone explain this question to me? I chose (A) at first, and I don't understand why (B) is right. I originally understood abuse of monopoly power is the only one that can reduce the competition, not the monopoly itself. Moreover, I don't understand why (A) is wrong. Could anybody go through this question and answer choices?

Thank you.