Answer:
1. a journal article titled "Marketing Strategies: Social Media" by a university professor
2. an article titled "Tips for Effective Social Media Marketing" on a government agency website
4. a business magazine article titled "Why Social Media Marketing Works" by a journalist
Explanation:
1 is credible because it was written by a professor at a university which makes him most likely credible. 2 is credible because its a gov website. 4 I'm not sure but if we have to pick 3 this would be it.