Thanks for the question! Let's take a bird's eye view of the question. Fear of retaliation makes would be aggressor nations hesitate, and people who scare off others have to have enough retaliatory power so the aggressor is deterred from attacking. (B) tells us that if the aggressing nation believes its own retaliatory power surpasses the defending nation, it won't attack. But it's actually the other way around - the attacking nation is likely to attack unless the defending nation has enough retaliatory power. Thus, (B) is wrong. Hope this helps!
