Which of the Following Would Be an Example of Social

Which of the following would be an example of social media?

A) political parties summarizing their campaign platforms on television
B) a public radio program that tells you where to go if you want to volunteer to work on a political campaign
C) a magazine that provides information on candidates' policy positions but also describes their family lives, hobbies, and favorite books
D) politicians using Twitter to communicate with their constituents directly