Longitudinal Research on IQ Change During Adulthood Indicates That

Longitudinal research on IQ change during adulthood indicates that

A) crystallized intelligence peaks in young adulthood and then declines steadily.
B) both fluid and crystallized and fluid intelligence peak in middle adulthood and then decline steadily.
C) crystallized intelligence peaks and then declines, while fluid intelligence remains steady into middle-old adulthood.
D) fluid intelligence peaks and then declines, while crystallized intelligence remains steady into middle-old adulthood.