下列物质中属于混合物的是 ____（填序号，下同），属于化合物的是 ____，属于单质的是 ____。

①空气 ②金刚石 ③高锰酸钾 ④水银

图一：一只失去雏鸟的美国红雀，总是给养鱼池边浮到水面张口求食的金鱼喂它捕来的昆虫，就像喂养自己的雏鸟一样，一连喂了好几个星期。

图二：很多年前，在英格兰有一只大山雀，一次偶然机会碰巧打开了放在门外的奶瓶盖，偷喝了牛奶。不久那里的其他大山雀也学会了偷喝牛奶。

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