How Did Early Brain Researchers Learn More About the Typical

How did early brain researchers learn more about the typical human brain?

A) through studies that examined hundreds of subjects who had moderate to severe memory problems
B) by altering the brains of human subjects and charting cognitive deficits that resulted from the alterations
C) through studies that examined hundreds of subjects who had moderate to severe learning problems
D) by examining individuals with specific brain lesions to learn what type of cognitive deficits resulted