The second within-subject factor is difficulty, included three levels, easy, medium and difficult.
第二个因素是被试内变量，即阅读材料的难度，分为容易、中等、难三个水平。
youdao
There are two game modes and three difficulty levels.
有两种游戏方式和三个困难水平。
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模块上移
模块下移
不移动