当河马张大嘴的时候，它是在打哈欠吗？

When hippo open its mouth wide, was it yawning?

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大概不是：当实验者张大嘴的时候，婴儿也张开嘴，但却没有吐舌头。

Probably not: when the experimenter opened his mouth, the infants responded with the same gesture, not by sticking their tongue out.

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最后，鹭鸶同意试试看，他让狼张大嘴，然后将长长的脖子伸进狼的喉咙，用尖嘴叼出骨头。

At last the crane agreed to try. It told the Wolf to open his mouth, and then put its long neck down the Wolf's throat.

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