If I remember correctly, this is a question for admission to a college in China long time ago:

1) You are traveling and have reached a point on the road where it diverges to Path A and Path B.  One path leads to Beijing and the other does not.

2) You were told by other people that at this point there is a restaurant boss who always tells the truth, and another restaurant boss who always tells a false statement.

3) You don't know which boss is which.  The two bosses know each other and know one always tell the truth and one always tells a false statement.

4) Now you can only ask one question to one boss that you choose, and be able to tell which path is to Beijing. (and it cannot be one question that actually contains two or more questions, and note that it is not one question to each boss, but just a total of one single question)  What is that question?