Craniometry Was Once Used as a Basis for Determining the Superiority

Craniometry was once used as a basis for determining the superiority of certain groups. What did craniometrists study?

A) The relationship between skull characteristics and displays of positive behavior to determine which cultural groups are the most capable.
B) The relationship between skull characteristics and intelligence
C) The impact on human behavior of drilling holes in the skull to relieve pressure on the brain
D) Variations within cultural groups on their head size to determine how to select capable leaders from within each group