Rumi and Shahid are both three months old. Rumi is highly active, easily irritated, and cries readily. Shahid is calm, adapts easily to change, and seems fearless. These differences illustrate __________.

A. the impact of shared environmental influences
B. how physical handicaps can have a genetic origin
C. differences in temperament
D. the fact that personality is influenced more by the environment than by genetics

Answer: C