F. C. Donders Developed His "Subtractive Method" To

F. C. Donders developed his "subtractive method" to:

A) subtract the image of the resting state of the brain in one PET image from the image of activity in a scan done following a cognitive activity, revealing where in the brain that activity was performed
B) empirically show how conscious mental processes depended on unconscious brain processes
C) measure the temporal duration of mental processes such as perceptual judgment
D) measure the speed by which neurons propagate action potentials