Answer:
C
Step-by-step explanation:
I don't see how A could apply. Piaget's theory has to do with the development of children. It has little to do with adults and teachers.
Standardized training can be done in the later stages, but it is ruinous in the early stages.
I think the answer is C. Piaget is all about education being child centered and methods and ideas cannot be introduced to a child before they are ready to know these things.
This is a higher mental activity and it can be done earlier, but there is some risk to it. C is still the best answer.