Answer:
B. Sharon solving a 6-piece puzzle on her own
Explanation:
As originated by Lev Givotsky(1896-1934), the zone of proximal development, abbreviated as ZPD (zona blizhaishego razvitiia, in original Russian), refers to the zone that is most closest and most immediate to the psychological development of the child including a range of emotional, cognitive, and psychological processes. It is also described in educational research of today as the difference between what a learner can do without help, and what they can do with assistance from a knowledgeable adult.