With Regard to Jean Piaget's Stages of Development, Modern Developmental

With regard to Jean Piaget's stages of development, modern developmental researchers have determined that:

A) most children learn cognitive skills noticeably later than Piaget assumed, a result that may be related to the fact the Piaget observed his own children.
B) the order of the stages of cognitive development is significantly affected by culture.
C) cultural factors appear to influence cognitive development and Piaget may have been biased in his conceptualization of "cognitive development."
D) within a given stage of development, performance on a wide variety of tasks is largely uniform and consistent.