Answer: A. 7-8 million years
Step-by-step explanation:
Chimpanzees are considered the closest species to humans and so a logical question to ask is why they haven't evolved as well or rather why they are still chimps and we are human.
The reason is that our ancestors split and went on different evolutionary paths. This split happened sometime 7 - 8 million years ago which therefore represents the years of cumulative evolution that separates chimpanzees from humans.