Answer:
d. Vygotsky's concept of the zone of proximal development
Step-by-step explanation:
Zone of proximal development: In psychology, the term "zone of proximal development" is also written as ZPD, and it was proposed by a social constructivist and soviet psychologist named Lev Vygotsky.
According to Vygotsky, it is described as the difference between the capability of a learner or a child to perform a particular task with the help of another person or guidance or without the help of anyone i.e, by oneself.
In the question above, the given statement signifies Vygotsky's concept of the zone of proximal development.