Difficulty is the backbone of a set of movement and the only factor to decide technical value score for a whole set of movement.

难度是一套动作的主干，是决定成套动作技术价值评分高低的唯一因素。

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Gymnastics scrapped its perfect-10 high score in 2006, replacing it with one that was supposed to remove some human error by instituting one score for the difficulty achieving certain moves, alongside a second, more subjective score for execution.

WSJ: London 2012: Chinese Men Take Gymnastics Gold