Which of these best describes why mainstream media might be called more “accountable” or “responsible” for reports?

Having a clear-cut procedures for dissemination of reports or information to the public.

Explanation:

What best describes why main stream might be called more accountable or responsible for reports is by making use of  clear-cut procedures or reliable source of information, for fact-checking and consequences for breaking these rules.

This enables the validity of the the information reported or given out. If for example, instance you are reporting on a recent events of a  statement made by politician , do not take this information from other sources like yahoo page, or Nairaland page or other sources.