在他的实验中，他把两个有盖的箱子放在几只狗的面前，其中一个箱子里放着食物，另个则空空如也。

In his experiment, dogs were shown two covered containers. One held a treat.

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在绿荫如盖的树旁有一个鱼塘。

There was a fish pond near the shady tree.

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在绿荫如盖的树旁有一个鱼塘。

There was a fish pond near the shady tree.

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