人类需要使用工具，因为他们没有像其他食肉动物如狮子和老虎那样锋利的牙齿。
Human beings needed to use tools because they did not have sharp teeth like other meat-eating animals, such as lions and tigers.
当走失的宠物被带到动物收容所时，那里的人们会使用一种特殊的工具来寻找微芯片，并读取它上的身份证号，然后他们会打电话给微芯片公司，以匹配号码与宠物的主人的信息。
When lost pets are brought to animal shelters, people there use a special tool to look for the microchip and read the ID number on it, then they'll call the microchip company to match the number to the information of the pet's owner.
通过使用类似这工具来获取骨髓这种动物躯体中最有营养的部分，他们开始培养起一个古老的良性循环。
Using tools like this one to obtain bone marrow, the most nutritious part of a carcass, they set in train an ancient virtuous circle.
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