Why are stone tools found on their own?

Stone tools are found on their own because generally the things that the stone tools were used on or attatched to have decayed or broken down over time

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Air enters through the nose (and sometimes the mouth), moves through the nasal cavity, the  pharynx, the  larynx, enters the  trachea, moves through the  bronchi  andbronchioles  till the alveoli.