Answer:
a)- frontal lobe
Step-by-step explanation:
Frontal lobe is present at front of each hemisphere and is the largest lobe in mammals. It controls cognitive skills in humans. These skills include judgement, language, emotional expression, problem solving, ability to communicate etc. Hence, it basically controls our personality.
After Zack's brain injury his personality changed. He became more critical and aggressive while earlier he used to be carefree and fun loving. Hence he has likely suffered damage to frontal lobe of his cortex.