Dr McCoy Is Attempting to Determine the Zone of Proximal

Dr McCoy is attempting to determine the zone of proximal development for Jabu when Jabu works on complex mazes. In order to do so, Dr McCoy must measure Jabu's personal performance on the maze and

A) Jabu's performance on several other Piagetian tasks.
B) Jabu's maze performance when assisted by a skilled helper.
C) Jabu's peers' performance on the same maze.
D) how well Jabu performed on the same maze earlier in his life.