The word "reciprocity" (Line 2, Para. 3) refers to ______.

A．It describes the children's inability of making peer friends.
B．It describes how to develop the friendship between the child and his parents.
C．It classifies the children's concept of making friends.
D．It classifies how a child considers his friends at different periods of life.

A．A failure to make friends with his peers.
B．A success in developing friendship among peers.
C．A failure to be friendly to the other children.
D．A failure to manage friendship skills.