In 2011,none of Roderick's Friends Owned a North Face Jacket

In 2011,none of Roderick's friends owned a North Face jacket and Roderick did not have a strong preference for North Face jackets.In 2012,many of Roderick's friends owned a North Face jacket,and Roderick did have a strong preference for North Face jackets.The change in Roderick's preferences from 2011 to 2012 can be best explained by the ________ effect.

A) winter
B) network
C) switching
D) duopolist
E) social