What Theory Is Best Supported to Explain Why Primates Evolved

What theory is best supported to explain why primates evolved such large brains?

A) They tend to eat foods that are rich in protein, which can support expansive neural development.
B) They tend to eat fruit and need to be clever enough to remember where the fruit trees were that would be ripe at each point in the season.
C) They tend to eat foods that require ingenuity to extract, such as nuts and termites.
D) They tend to live in large social groups, which requires intelligence to function effectively.
E) The number of males and females is unequal, so individuals need to outsmart their competitors to attract mates.