Twenty-Five-Year Old Lay Hoon Took a Battery of Intelligence Tests

Multiple Choice

Twenty-five-year old Lay Hoon took a battery of intelligence tests for admission into the Royal Hong Kong Air Force Academy and scored slightly above average. She was tested again twenty years later, and her performance on the tests nearly doubled. According to the text, Horn and his colleagues would attribute this increase to

A) an increase in fluid intelligence.
B) an increase in crystallized intelligence.
C) an increase in both fluid and crystallized intelligence.
D) an increase in concentration and reaction time.