Which of the Following Was a Finding of Kail's 1990

Which of the following was a finding of Kail's 1990 research on children's cognitive development?

A) That younger children's short-term memories are more limited than those of older children.
B) That Piaget greatly underestimated the abilities of younger children.
C) That older children's long-term memories are more accurate than those of younger children.
D) That Vygotsky's concept of the zone of proximal development was only applicable to the memory of younger children.