What Has Traditionally Been the Main Reason for the Characterization

What has traditionally been the main reason for the characterization of the left hemisphere as the "dominant" hemisphere

A)  evidence that the left hemisphere usually processes complex information 
B)  evidence that the left hemisphere usually processes language 
C)  the fact that the majority of people are right-handed 
D)  evidence that patients use only their left hemisphere for processing information after split-brain surgery