What is the difference between fluid and crystallized intelligence, and how do these typically trend in early adulthood?

What is the difference between fluid and crystallized intelligence, and how do these typically trend in early adulthood?

• A. Fluid intelligence is accumulated knowledge; crystallized is abstract reasoning.
• B. Fluid intelligence grows with age; crystallized declines with age.
• C. Fluid and crystallized intelligence are the same; no change in adulthood.
• D. Fluid intelligence involves novel problem solving and processing speed; crystallized involves accumulated knowledge and skills; fluid peaks earlier and declines slowly, while crystallized increases with education and experience.

Answer: (D)