According to Vygotsky, the most developmentally significant form of play is:

Concept

In Vygotsky’s sociocultural theory, mature make-believe or imaginative play creates an imaginary situation governed by roles and rules.

While acting beyond immediate impulses and everyday behaviour, a child practises self-regulation, symbolic thinking, and socially shared meanings; play therefore creates a zone of proximal development.

Application

The stem asks for the form of play with the greatest developmental significance. Among the listed choices, imaginative play matches Vygotsky’s account because the child represents situations symbolically and follows the rules implicit in an adopted role.

Contrast

• Solitary play describes whether a child plays alone; it does not identify Vygotsky’s central developmental mechanism.

• Functional play centres on repetitive sensory-motor actions with objects rather than an imaginary role-governed situation.

• Rule-based play makes explicit rules prominent, but Vygotsky’s classic early-childhood account treats make-believe play—with implicit role rules—as the leading developmental form.

Result

Therefore, the best-supported offered answer is imaginative play.