When a child can simultaneously manipulate two dimensions cognitively, such as circumference and thickness, so that s/he understands that a change in one dimension is compensated for by a change in the other, s/he understands?
The correct answer is reciprocity. Reciprocity is being
defined as a practice of being able to exchange things with others for the
purpose of privileges or mutual benefit by which can be granted by another
party, organization or the country.
