Piaget Believed That the Exact Timing of a Stage Reflected

Piaget believed that the exact timing of a stage reflected an interaction between which two aspects of an infant's experience?

A) level of physical maturation and the social environment in which the child is raised
B) level of physical maturation and the genetic predisposition of the child
C) level of cognitive development and the experiences that are provided by the child's genotype
D) level of physical maturation and cognitive development of the child