Spearman Inferred the Existence of a "G" Factor in Intelligence

Spearman inferred the existence of a "g" factor in intelligence because of his evidence that, on the average,

A) people who live in prosperous countries do better on IQ tests than those in poorer and less educated countries.
B) each generation of people scores higher on IQ tests than the last generation.
C) people who do well on a test of one ability also do well on tests of other abilities.
D) high-IQ parents tend to have high-IQ children.