Concept:Political socialization is the process by which people learn political values and attitudes from various agents.Explanation:The main agents of political socialization are the family, school, media, peer groups, and political parties.A political party is an important agent because it organizes citizens, shapes their political opinions, and encourages them to participate in elections.The other options are not full agents: a party structure or constitution is just an internal framework, and an electoral college is only a voting body.Answer:B. political party