The accompanying figure shows that humans have thicker thumb metacarpals than chimpanzees or bonobos,with broader heads.This is directly correlated with humans' ________.

A) bar-shaped central portion of the hyoid bone
B) increasing dependence on meat in the diet
C) more elaborate thumb musculature and better precision grip
D) loss of the ability to knuckle-walk
E) loss of an arboreal (tree-based) lifestyle