Which of the Following Would Be the Best Example of Development

Which of the following would be the best example of development according to the guided participation perspective?

A) Amos can play the piano beautifully at home but has problems playing in front of his peers at school.
B) Tammy moves from watching her family dig clams to digging in the sand with her older brother to actually finding clams on her own.
C) Marcus and Colin work together to solve a math problem that neither of them could solve individually.
D) Enrique moves from talking out loud to whispering to himself to silently moving his lips as he ties his shoes.