A criticism of Piaget’s concrete operations period is apparent in the longitudinal data collected by Tomlinson-Keasey and colleagues, which is that _______

a. younger children are fully capable of solving all of Piaget’s concrete operations tasks
b. there is a stage-like jump to high levels of performance at ages 6 to 7, rather than 7 to 8 as Piaget claimed
c. children reach a ceiling level of performance on Piaget’s tasks, and do not appear to proceed to full mastery in middle childhood
d. acquisition of concrete operational concepts is gradual rather than stage-like

Answer: D