They also looked at pictures of a leaf, shell, or rock.

他们也观看树叶，贝壳或石头的图片。

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When they have reached the size they want, they use an implement such as a rock or shell to smooth the surface of the pot.

参考译文：做出想要的尺寸时，他们用一个工具，比如一块石头或贝壳，将罐子的表面弄平滑。

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In one experiment 3-year olds looked at pictures of a fork, teddy bear, truck, and other human-made objects. They also looked at pictures of a leaf, shell, or rock.

在一项实验中，让一些三岁的孩子去看叉子、泰迪熊、卡车和其他一些人造的东西的图片，也让他们看树叶、贝壳和石头的图片。

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On federal lands, Shell has been researching methods to cook oil out of the shale (basically oil-soaked rock) without mining it or polluting groundwater.

FORBES: OutFront