14. After class, one of the five students wrote a dirty word on the blackboard. When the teacher questioned them, the students answered as follows:
A said: “It was B or C.”
B said: “It wasn't me or E.”
C said: “Both of them are lying.”
D said: “No, only one of A or B is telling the truth.”
E said: “No, D is lying.”
The teacher knows that three of the students never lie, while two of them always lie. Please determine who wrote the word on the blackboard based on this information.
【Analysis】E says D is lying, so among D and E, at least one is lying. C says A and B are both lying, so among A, B, and C, at least one is lying. Therefore, among D and E, exactly one is lying, and among A, B, and C, exactly one is lying. Clearly, the liar among A, B, and C must be C. If C is telling the truth, then among A, B, and C, there would be two liars, which is a contradiction. So C is lying, and A and B are telling the truth. Therefore, D is lying, and E is telling the truth. A says it was written by B or C, and B says it wasn't him, so the writing on the blackboard was done by C.