Mara purchased a shape sorter for her 9-month-old daughter, lucia. mara notices that lucia picks up the shapes but has difficulty dropping them into the correct slots. mara hands a shape to lucia and guides her hand to the correct slot, slowly turning the shape until it fits. after some practice with mara, lucia is able to retrieve a shape and twist it until it fits into the slot. mara's assistance is consistent with which of the following concepts?
a. vygotsky's zone of proximal development
b. piagetian schemes
c. the information-processing perspective
d. bandura's social learning