Jean Piaget’s theory of cognitive development implicates that:

Piaget's stage theory of cognitive development holds that children progress through distinct, age-related stages (sensorimotor, preoperational, concrete operational, formal operational), each marked by qualitatively different ways of thinking. Effective instruction must therefore be developmentally appropriate — matched to a learner's current stage and reasoning capacity — rather than driven by external reinforcement or a fixed content sequence.

Applying this principle here: since a child's cognitive readiness changes with age and stage, curriculum design must be built around the learner's age-group and developmental stage so that concepts, tasks, and materials suit what the child can meaningfully process at that point — exactly what the keyed option states.

• Conditioning behaviour through rewards and punishments describes operant conditioning (behaviourism), an externally driven framework distinct from Piaget's internally driven, stage-based cognitive construction.

• Teaching complex concepts before simple ones reverses Piaget's actual developmental progression, where reasoning moves from concrete, simple ideas toward abstract, complex ones as a stage matures.

• Judging teaching only by the outcome of an activity ignores Piaget's central emphasis on the process of thinking — how a child reasons and constructs understanding — not merely the end result.