What can we infer from the last paragraph？[A] Monkeys can be trained to develop social

What can we infer from the last paragraph？

[A] Monkeys can be trained to develop social emotions.

[B] Human indignation evolved from an uncertain source.

[C] Animals usually show their feelings openly as humans do.

[D] Cooperation among monkeys remains stable only in the wild.

请帮忙给出正确答案和分析，谢谢！