A box contains blue marbles. Another two boxes contain only white marbles.  Label on Box $$\rm A$$: white marbles  Label on Box $$\rm B$$: blue marbles  Label on Box $$\rm C$$: Box $$\rm B$$ contains blue marbles  Which box contains blue marbles if two of the above labels are wrong?． 
Overseas Competition->Knowledge Point->Combinatorics->Logical Reasoning->Reasoning using Hypothesis
If two of the labels are wrong, \textbf{one label is correct.}  If the label on Box A is correct, Box A contains white marbles.  The label on Box B is wrong, so Box B contains white marbles.  The label on Box C is wrong, so Box B contains white marbles.  Therefore, Box A and Box B contain white marbles, while \textbf{Box C} contains blue marbles. 