A major accident occurred in a large coal mine, and the personnel at the scene of the accident made the following judgments: Miner A: The cause of the accident was equipment problems; Miner b: someone violated the operating rules, but the cause of the accident was not the equipment problem; Miner C: If the cause of the accident is equipment problems, then someone has violated the operating rules; Miner Ding: The cause of the accident was equipment problems, but no one violated the operating rules.

Question: If only one of the above four people is true, who is it?

Explanation: Miner B is real. Hypothesis method can be used. If A is true, then at least one of C and D is correct and only contradicts one person's truth, so A can't tell the truth, and so on, only B is judged to be true.

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