Sherlock Holmes was walking down the corridor. Suddenly he heard a woman screaming, “Please, John, don’t kill me!” A shot rang. Holmes burst into the room. In one corner lay a dead woman and a gun. In another corner stood a postman, a lawyer, and an accountant. Sherlock looked at them, approached the postman, and grabbed him: “I will arrest you for killing this woman.” It was really the postman who killed this woman, but how could Holmes know it?
The postman was the only man. The lawyer and the accountant were women.