Final answer:
The range of tasks that are too difficult for children to master alone but can be learned with guidance and assistance is called the Zone of Proximal Development (ZPD).
Step-by-step explanation:
The range of tasks that are too difficult for children to master alone but that can be learned with the guidance and assistance of adults or more skilled children is called the Zone of Proximal Development (ZPD). According to Piaget, children go through different stages of cognitive development where they gradually acquire new skills and knowledge. ZPD represents the range of tasks that a child can do with assistance, bridging the gap between what the child can do on their own and what they can do with help. For example, a child might be able to count up to 10 independently but can count up to 20 with the guidance of an adult or older sibling.