学校的停车场上，警报响彻天空。

In the parking lot of the school, the siren filled the air.

《柯林斯英汉双解大词典》

然而，当我到学校的时候，天空突然乌云密布，而且开始打雷。

However, when I got to school, the sky turned to be gray with the gloomy clouds as well as thunder.

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学校的天空依然是不带杂质的蓝，连云彩都很少。

Schools in the sky is still blue without impurities, even the clouds are few.

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