Answer:
A large brain allows humans to solve complex problems.
Step-by-step explanation:
The large brain in humans has enabled them to solve a complex problem in of the real world and also enabled them to survive more as compared to humans with the smaller brains.
In seven million years the size of the human brain is tripled. That allows them to store and process a huge amount of information and also help to interact with the people in the surrounding better.
Hence, the correct answer would be option B.