通常，滑雪者或滑雪运动员在避暑山庄留心索道的唯一时刻就是其中一个不能使用的时候。

Usually, the only time skiers or snowboarders notice the lifts in a mountain resort is when one of them doesn't work.

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随着他的刻刀或剪刀切开纸张，他时刻留心正负形状间的关系。

As his knife or scissors cut into the paper, he is constantly aware of the relationship between positive and negative forms.

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