A gas explosion occurred in a coal mine  Coal mine personnel have the following conclusion: duty director: the cause of the accident is the operation problem  Miner 1: it is true that some people have violated the safety regulations, but the cause of the accident is not operational problems  Miner 2: if the cause of the accident is an operational problem, then someone has violated the safety regulations
Safety officer: the cause of the accident was operational problems, but no one violated the safety regulations
Miner 2's assertion was true and no one violated safety regulations