A bag of incense money was lost in the monastery. The abbot found three young monks, A, B and C, to inquire. The three men stated one by one, and A said, I didn't steal it. B said, A stole it. C said, I didn't steal it. D, who was on the side, learned the truth and commented, only one of you stole it, and only one of you was right.
 A stole the incense money.