The answer is: B. Machiavelli forces readers to carefully consider the meanings of the words merciful and mercy.
Machiavelli explains in this passage that being merciful is not necessarily a good thing when it allows for bad things to happen to the collectivity. Being too merciful might mean your people will have to suffer the consequences of your soft heart, according to the author.
That reflection is probably surprising to most readers, who think of mercy as kindness and forgiveness. Machiavelli tries to make people see it from his point of view: mercy in itself is not bad but, if wrongly and excessively applied, might end up causing more harm than good.