According to Lev Vygotsky, children benefit from the experience of interacting…

Lev Vygotsky's socio-cultural theory holds that cognitive development is fundamentally social: children advance not just through solitary activity but through guided interaction with a "more knowledgeable other" (MKO) - a person with greater skill or understanding, such as a teacher, parent, or capable peer. The zone of proximal development (ZPD) is the gap between what a learner can do alone and what the same learner can do with such guidance; Vygotsky held that learning is maximised specifically inside this zone, where a task is too hard to do unaided but achievable with support (scaffolding).

Applying this to the two blanks: the first blank names the social agent Vygotsky emphasised - a more knowledgeable other, not the physical environment (unmediated exploration of objects or surroundings is closer to Piaget's account of development). The second blank names where that guided interaction is most productive - within the zone of proximal development, i.e. on tasks the child cannot yet manage alone but can manage with assistance. A task lying just outside the ZPD remains beyond even guided reach and does not produce the same developmental gain, so it does not fit Vygotsky's account of effective scaffolding.

Contrasting the other pairings against Vygotsky's own formulation:

• A pairing of "more knowledgeable others" with "just outside" keeps the right kind of social agent but places the benefit beyond the zone that guided effort can actually close.

• A pairing of "the physical environment" with "within" keeps the right zone but substitutes unmediated surroundings for a person of greater skill as the driver of growth.

• A pairing of "the physical environment" with "just outside" combines both mismatches at once.

Hence the pairing that matches Vygotsky's own formulation is guidance from a more knowledgeable other, occurring within the zone of proximal development.