Final answer:
A child is working in their zone of proximal development when they are able to accomplish a task with the help of a skilled person, which aligns with Lev Vygotsky's theory that learning is enhanced through social interactions within the ZPD.
Step-by-step explanation:
When a child attempts a task and is unable to do it alone, but succeeds with the help of a person skilled in the task, the child is working in his or her zone of proximal development. This concept was introduced by the psychologist Lev Vygotsky and refers to the difference between what a learner can do without help and what they can achieve with guidance and encouragement from a skilled partner. Vygotsky's theory asserts that learning is a social process and cognitive development is limited to a certain range at any given age. The zone of proximal development (ZPD) is where the learner is challenged just beyond their current capability, emphasizing that the role of a person skilled in scaffolding the child's learning is crucial.