All of the Following Have Been Found in Studies of Peer

All of the following have been found in studies of peer relationships and friendships except

A) firstborn children's friendships may help buffer negative effects of the birth of a sibling
B) peers and friends tend to play together more and have more conflicts than do siblings
C) children tend to be more cooperative and flexible when interacting with friends than with siblings
D) parents play an important role in the development of their children's social competence with peers