One Reason That Early Research on Specific Human Cognitive Capacities

One reason that early research on specific human cognitive capacities and the brain areas that are responsible for them developed rather slowly before the twentieth century is that

A) most early investigators were limited to postmortem studies to localize lesions.
B) investigators did not know the brain was separated into two hemispheres until the twentieth century.
C) most early investigators focused on studying the brain-behavior relationship in animals rather than in humans.
D) there was little interest in this field until the twentieth century.