Correct option is C
Jean Piaget and Lev Vygotsky indeed had differing perspectives on the influence of language on cognitive development in children, making statement A true. Piaget's theory emphasizes the development of language as a result of cognitive development, while Vygotsky believed that language plays a fundamental role in the development of cognitive abilities. Therefore, their approaches to how language influences cognitive development are notably different.
Statement R, regarding discovery learning, is also true. Discovery learning is a method where students learn by doing and experimenting, and the teacher's role is to provide opportunities and guidance rather than direct instruction. However, R is not the correct explanation of A because it is related to a teaching method and does not directly explain the differing perspectives of Piaget and Vygotsky on language and cognitive development. Therefore, option (c) "Both A and R are true, but R is not the correct explanation of A" is the correct answer.