The correct sentence is:
Each person’s brain develops and forms new connections, but it is not aware of these changes.
The antecedent of the pronoun "it" is "each person’s brain".
Vigilant means like cautious
lighthearted means like amusing and entertaining
so I would say its Vigilant
I hope I helped!
Answer:
it's basically about two grown men who are close friends and they're working for their dreams during the Great Depression
