I believe the answer is D) a social movement.
In their study Lieberman and Morelli used FMRIS to help them study people reactions when<span>looking at people's sad image.
FMRIS is used to observe brain activity that caused by the blood flow within areas of the brain.
Lieberman and morelli showed the test subjects with various type of pictures that target specific emotions in order to see which part of the brain is responsible for that emotion.</span>
