The piece of evidence that best demonstrates a link between brain function and kindness is:
A. "We know that deciding to be generous or cooperating with others activates an area of the brain called the striatum. Interestingly, this area responds to things we find rewarding" (Paragraph 2)
This statement specifically connects the act of being kind (generous or cooperative) to the activation of a particular brain area (the striatum), indicating a biological basis for the feelings associated with kindness.