As far as I know the whole brain changes, but since you're looking for a considerable development, the answer would definitely be the third option.
The prepfrontal cortex is located behind our forehead and is responsible for the cognitive and logical thinking.
Answer:
[tex] \boxed{\bf~The~answer~is~C.~(Prefrontal~Cortex).} [/tex]
Hope it helped,
Happy homework/ study/ exam!
