Piaget believed that are schemes reflecting an infant's repetition of interesting or enjoyable actions that focus on the infant's own body. An example of this might be an infant putting its thumb in its mouth and sucking.

Primary circular reactions

Explanation:

Piaget believed that Primary circular reactions are schemes reflecting an infant's repetition of interesting or enjoyable actions that focus on the infant's own body. An example of this might be an infant putting its thumb in its mouth and sucking. Primary circular reactions is a substage that involves coordinating sensation and new schemas, For example, a child may suck his or her thumb by accident and then later intentionally repeat the action, these actions are repeated because the infant finds them pleasurable .

the answer to your question is,

d. when a child was born.

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