Concept:Vygotsky's sociocultural theory states that social interaction and language are central to cognitive development.Explanation:Vygotsky argued that language and thought are closely linked. As children acquire language, it reshapes how they think and solve problems. Language allows them to internalize social experiences and use self-talk to guide actions. This shows that language development fundamentally changes the nature of human thought. In contrast, the other options contradict his views: he emphasized interaction with adults and peers (not isolation), rejected a biological language device (Chomsky's idea), and highlighted culture's strong role.Answer:C. language development changes the nature of human thought