Cattell's Idea That There Are Two Types of Main Intelligences

Cattell's idea that there are two types of main intelligences, crystallized (acquired) and fluid (innate) , came from:

A) his animosity toward the Eugenics movement and his personal belief that cultural factors and learned behaviors must play a part in intelligence.
B) his research on brain activity.
C) his research on child development, especially twin studies.
D) his observations that as cultural factors were removed from intelligence tests, marked changes were seen in test scores.