According to Lev Vygotsky's concept of the zone of proximal development (ZPD), learning is

• A. Achieved by discovering which answers will lead to rewards.
• B. Achieved by assimilating new understandings to accommodate the demands of the world.
• C. Affected by how the environment and genetically programmed learning ability interact during a critical period.
• D. A social activity between a less knowledgeable child and another adult or child who is more knowledgeable.