"With an appropriate question / suggestion, the child's understanding can be extended far beyond the point which she could have reached alone." Which construct does the above statement highlight?

The Zone of Proximal Development (ZPD), introduced by Vygotsky, refers to the gap between what a child can do independently and what they can achieve with guidance from a more knowledgeable other. The statement describes exactly this concept - extending a child's understanding through appropriate scaffolding (questions, suggestions) beyond their independent capacity.