52. What does Raviv say about the four different kinds of variability?
A) Which of them is most relevant to the task at hand is to be confirmed.
B) Why they have an impact on learning is far from being understood.
C) Why they have never been directly compared remains a mystery.
D) Which of them is most conducive to learning is yet to be identified.
（本题出自2024年6月六级真题卷三）
答案&解析
52.D）
文章第五段首句提到了四种不同的可变性，接着引用雷维夫的话，“这四种可变性从未被直接比较过——这意味着我们目前不知道哪一种对学习最有效。”选项D是对该句话的同义转述，故为正确答案。选项A在原文中未提到，故排除。选项B、C是根据原文中的词语effective for learning、been directly compared设置的干扰项，故都排除。
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