Step 1: Read the clue closely.
The person gives out information about a secret event or a scandal and does so to the media. The act is a form of exposure of hidden wrongdoing.
Step 2: Think of the standard term.
In journalism such an insider source is called a whistleblower. Many news stories on corruption started with one.
Step 3: Test the other titles.
An inspector investigates, an arbitrator settles disputes and a social worker supports welfare. None of them is defined by leaking to the press.
Step 4: Choose.
The answer is option 3, because the description and the title match.
Extra check: Why the other options fail.
A tip for such questions: look for the word that stands for the act in the clue. Divulging a secret in the public interest is whistleblowing. Policing, arbitration and social work are all real jobs, but none of them is about exposing hidden matters to the media, so options 1, 2 and 4 are not suitable.
Final Answer:
The correct term is whistleblower, option 3.
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