Why Is the Unusual Case of Phineas Gage Instructive for Understanding

Why is the unusual case of Phineas Gage instructive for understanding the relationship between personality and the brain?

A) Gage was born without a frontal lobe and, correspondingly, lacked any sense of conscientiousness.
B) It was the first demonstration of how an alteration in personality could lead to deterioration of brain tissue.
C) Gage agreed to a full-scale examination of his brain structures, which identified the brain areas associated with each of the Big Five personality traits.
D) It presented a rare opportunity to see how radical changes to the physical brain affect observable personality characteristics.