Regarding Piaget's Concept of the Formal Operational Stage, More Recent

Multiple Choice

Regarding Piaget's concept of the formal operational stage, more recent studies have shown that

A) children enter this stage much earlier than the age proposed by Piaget.
B) children enter this stage significantly later than the age proposed by Piaget.
C) it is not actually a stage of its own but rather part of the concrete operational stage.
D) it is not achieved by all people and probably not even by most people in the world.