According to Piaget's Cognitive Developmental Theory, in the first habits and primary circular reactions substage, the main focus is on:

• A. Solving problems through trial and error with external objects
• B. Coordinating vision and touch to reach for objects
• C. Engaging in pretend play and using symbols
• D. Repeating actions centered on the infant's own body, such as sucking their thumb

Answer: (D)

Verified step by step guidance

1. Understand that Piaget's Sensorimotor Stage (birth to 2 years) is divided into substages, each characterized by different cognitive abilities.
2. Identify that the 'first habits and primary circular reactions' substage occurs approximately between 1 to 4 months of age.
3. Recognize that during this substage, infants focus on repeating actions that involve their own body, such as thumb sucking, which are called primary circular reactions.
4. Distinguish these actions from later substages where infants begin to coordinate vision and touch or engage in trial and error with external objects.
5. Conclude that the main focus in this substage is on repeating pleasurable actions centered on the infant's own body, rather than interacting with external objects or symbolic play.