The case of Phineas Gage, a railroad worker who survived after a metal bar passed through his brain, offered insights about brain functions. Similarly, some researchers remove parts of the brain in animals to observe changes in behavior or study individuals that have experienced stokes that damage parts of their brains. These studies rely on:

These studies rely on: LESIONS

Explanation:

Lesions that are found on the brain are defined as part of the tissues found in the brain that has been damaged because of injuries to the brain or a disease.

When lesions are found on the brain, the damages to the brain is usually permanent but some of the effects of the lesions can be managed effectively through medical rehabilitation.

Take for example the case of Phineas Gage who was a railroad worker that was severely injuried when a metal bar he was working on due to an explosion penetrated and exited his brain and caused a severe damage to his left frontal lobe. He survived but due to the lesions on his brain i.e. damage to the tissues of his left frontal lobe he experienced changes in his behaviour and personality.

Due to the incident with Phineas Gage, this led to tremendous discovery in the field of neurology as people began to study, understand and observe that there are certain parts of the brain that are responsible for carrying out specific functions in the body.

it should be d or b but i'm sure it's d