The prince of a small kingdom travels to a neighboring land to meet with their king. After the meeting, he agrees to take one of the king's daughters' hand in marriage. The prince is told:
- Princess Anne always tells the truth.
- Princess Beatrice always lies.
- Princess Catherine speaks randomly.
The prince gets to meet the 3 princesses at the same time, but unfortunately they are identical triplets and he cannot tell them apart. He may ask one of them a yes or no question. If he asks a question that she cannot answer, then he will be executed for rudeness. After that, he must choose a bride.
The prince is happy to marry Anne or Beatrice, but does not want to marry Catherine since he will never know what she is really thinking. How should he proceed?