3. (10 points) Xiao Dong, Xiao Xi, Xiao Nan, and Xiao Bei, four friends, were playing a game together when they found a red scarf and handed it to the teacher. The teacher asked who found it? Xiao Dong said it wasn't Xiao Xi; Xiao Xi said it wasn't Xiao Nan; Xiao Nan said what Xiao Dong said was incorrect; Xiao Bei said what Xiao Nan said was also incorrect. Only one of them was right, and this person is ( )
A. Xiao Dong
B. Xiao Xi
C. Xiao Nan
D. Xiao Bei
【Analysis】According to the problem statement “Xiao Dong says it's not Xiao Xi; Xiao Xi says it's not Xiao Nan; Xiao Nan says what Xiao Dong said is incorrect; Xiao Bei says what Xiao Nan said is also incorrect.”, from the dialogue, we can see that what Xiao Nan and Xiao Bei said are contradictory, so one of them must be correct. Therefore, Xiao Dong must be wrong. Since Xiao Dong is wrong, Xiao Nan must be right.

【Solution】According to the analysis of the problem statement, Xiao Nan and Xiao Bei's statements are contradictory, so one of them must be correct. Assuming Xiao Bei is correct, then Xiao Nan saying “what Xiao Dong said is incorrect” would be wrong, which means Xiao Dong is right. This contradicts the given condition that only one person is correct, so this assumption is invalid. Therefore, Xiao Nan is correct.

The answer is: $C$.