Other Things Being Equal, Which One of the Following Four

Other things being equal, which one of the following four boys is likely to learn and remember the most by reading a book about spiders?

A) Eight-year-old Albert, who knows a lot more about spiders than the other boys do
B) Eight-year-old Bernard, for whom the book is slightly above his zone of proximal development
C) Ten-year-old Colt, who performs well on a task involving conservation of weight
D) Ten-year-old Darren, who shows some understanding of simple proportions