A serious safety accident occurred in a coal mine  As for the cause of the accident, the four responsible persons A, B, C, and D have the following conclusions: A: If the direct cause of the accident is equipment failure, then someone must have violated the operating rules  B: It is true that someone has violated the operating rules, but the direct cause of the accident is not the equipment failure  C: The direct cause of the accident is indeed the equipment failure, but no one has violated the operation
D: The direct cause of the accident is the equipment failure
A is true, but no one violated the rules of operation