在测试程序中，我们增加了一个鼠标滚轮侦听器，它让背景色按照某一方向在颜色数组中循环，如清单4所示。

In the test program, we'll attach a wheel listener that has the background color loop through the array of colors based upon the direction, as shown in Listing 4.

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搬迁和拆除的循环已经变成首都永恒的背景。 在北京为2008年奥运作准备的阶段，此风尤盛。

That cycle of relocation and demolition has become a constant backdrop in this capital -- never more so than in the year leading up to Beijing's hosting of the 2008 Olympics.

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现在选择所有的循环背景音乐片段。

Now select all looping background music clips.

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