Step 1: Look at the key word.
The word arbitrates means to judge a dispute between two sides. Here the sides are the newspaper and a complaining reader.
Step 2: Find who is neutral.
A person who judges must be impartial. The staff roles in options 1 to 3 are all part of the news production chain.
Step 3: Rule out the production staff.
The wire editor handles agency copy, the sub-editor polishes copy, and the reporter writes the story. None of them sits above the newsroom to judge fairness.
Step 4: Find the specialist.
An ombudsman is appointed to take reader complaints and look into them independently. This is the exact role in the question.
Step 5: Conclude.
So option 4 is the answer.
Step 6: Memory aid.
As a memory aid, an ombudsman is the same kind of independent judge that other organisations use for public complaints. In newspapers this person is often called the readers' editor. Staff who write or edit copy cannot judge their own work fairly.
Final Answer:
Only the ombudsman has the job of arbitrating complaints.
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