Final answer:
The word that completes the sentence the best is 'motes', as it refers to small particles or specks of sand.
Step-by-step explanation:
The word that completes the sentence the best is motes. In this context, 'motes' refers to small particles or specks of sand. It makes sense to find motes of sand in your hair weeks after going to the beach, as they can easily get trapped in your hair and be difficult to completely remove.
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