Answer:
The phrase "whose selfishness had not hesitated to buy its own peace at the price, perhaps, of the existence of the whole human race" best supports the the that humans posses the ability to be monstrous. The phrase shows how humans are only thinking of what they want and need and not about how their voices affect the people and things around them.
The pronoun for the sentence is D.object
Glad to help you ^-^
There are about 4, but I think the most important are~
To persuade and to inform.
