Read this sentence.

Some biologists, including Richard Dawkins, have argued that human nature is inherently, absolutely competitive and that perceived altruism is never really altruistic; it merely hides self- serving purposes.

Which of the following statements best paraphrases the ideas in this sentence?
a. Biologists have argued whether humans put more value on being unselfish or being the best at something.
b. Biologists are in disagreement about whether it is human nature to be altruistic or competitive.
c. Some biologists argue that humans are altruistic by nature even though it is often thought to be self-serving.
d. Some biologists believe that altruism in humans is always egotistical in nature, and competition is our natural state.