In Most Elementary School Curriculum,mathematical Variables First Appear in the Sixth

Multiple Choice

In most elementary school curriculum,mathematical variables first appear in the sixth grade.In the context of Piaget's theory,which of the following best supports this trend?

A) Children in the concrete operational stage cannot reason with hypothetical entities such as variables.
B) According to Piaget,children in the concrete operational stage are too egocentric.
C) Children are incapable of understanding the idea of reversibility until the beginning of the formal operational period.
D) Dealing with variables requires mastering the principle of conservation,which does not usually appear until adolescence.