Final answer:
The king's power best reveals the lose-lose situation in 'The Lady or the Tiger' as it forces a dire outcome regardless of the chosen door, with no regard for personal autonomy or feelings.
Step-by-step explanation:
The piece of evidence that best reveals the lose-lose reality of the king's arena in "The Lady or the Tiger" is B) The king's power. This is because the king's authority ensures that whichever door the accused person opens, the outcome is grim. If the door with the lady is chosen, the accused marries immediately without a choice in the matter. If the door with the tiger is chosen, it results in a violent death. Therefore, the individual is at the mercy of the king's judgement and loses some degree of autonomy regardless of the outcome. An example that highlights the king's overbearing control is his reaction upon discovering his daughter's lover. Instead of considering his daughter's feelings, he exercises his power by subjecting the lover to the trial of the arena.