अधिगम सिद्धांत में 'क्रियाप्रसूत अनुबंधन' (Operant Conditioning) की अवधारणा किसके द्वारा प्रतिपादित की गई थी?

Which of the following is an example of meaningful learning?

In the context of operant conditioning and learning theories, reinforcement primarily refers to:

The concept of 'Zone of Proximal Development' (ZPD) was introduced by which theorist as a part of socio-cultural learning and development theory?