When this question involves three different roles: thief, good man and accomplice, there are six kinds of guesses (1*2*3=6 kinds, which is the factorial principle, and the fourth grade of primary school does not need to know). First of all, A is a thief, B is an accessory and C is a good man. Then everything C said was true, while everything A said was false. Both of them said that B was a driver. Obviously, this guess is wrong. At the same time, the second guess is ruled out: A is a good man, B is an accessory, and C is a thief. The third is: A is an accomplice, B is a thief, and C is a good man. Then what B and C say is definitely different, but they all say that C is a salesman in a department store, which rules out this speculation. At the same time, the fourth guess is ruled out: A is an accessory, B is a good man, and C is a thief. There are only two kinds of guesses now. It is said that C is an accessory, so what C said can't be doubted, let alone convincing. The fifth guess is: A is a good man, B is a thief and C is an accessory. But the sentence "A, if you ask him, he will definitely say that he is a salesman" really happened to A. He can't be a thief, and his fifth guess was rejected again. Now there is only one guess: A is a thief, B is a good man, and C is an accessory. He is the right answer, but the answer in the book is wrong.