Correlational Research Has Found Differences in the Brains of Those

Correlational research has found differences in the brains of those with high IQs as opposed to low IQs.What is the most likely reason for these findings

A)  The differences observed are clearly due to genetics. 
B)  The differences may be due to environmental factors which impacted the brain during the process of its development. 
C)  Smart people are superior to those with low IQs by way of their biological inheritance. 
D)  There was a malfunction in the brain imaging technology and the results were tossed.