Final answer:
The media effect best demonstrated by a chart tracking the number of stories on gun control is agenda setting. Agenda setting describes how media coverage can influence the public’s perception of important issues, signaling to politicians what voters find significant.
Step-by-step explanation:
The question is asking which media effect is best demonstrated by a chart tracking the number of media stories on gun control between February and May 2018. Among the options given (agenda setting, priming, cultivation, and filtering), the answer is agenda setting. This is because agenda setting refers to the media's ability to select and emphasize those issues that they feel deserve public attention, which in turn influences the public's perception of what is important.
For example, if the media covers gun control extensively, it signals to the public and policymakers that this is a crucial issue. This can shape the policy agenda and influence what politicians believe is of national importance, as they may think that voters find the issue significant due to its frequent coverage.
Thus, when considering the influence that media coverage has on the public's opinion and the political agenda, especially in terms of national issues, agenda setting is the media effect best demonstrated by the chart in the given scenario.