‘Marketing Mix.” Please respond to the following: When  thinking about the history of public relations, determine which  development do you think was the most significant. Explain your  reasoning.  Of all the articles you found on the Web site for the World Advertising Research Centre (WARC) at http://www.warc.com/, determine which was the most applicable.  Explain your rationale.  Explain how can this information help you communicate effectively with these professionals.