In Primary Somatosensory Cortex There Are More Regions of Integration

In primary somatosensory cortex there are more regions of integration associated with the fingers, lips and feet than any other body part. Why does this make sense?

A) those areas cover more relative surface area compared to other body parts
B) those body parts exchange with the environment more than other parts
C) those body parts move the most
D) those areas feel more pain than other areas so the brain is more sensitive to them