Puddle puzzle
My cat used to drink from the garden pond and never seemed to suffer any ill effects, and you often see dogs drinking from muddy puddles. So why do humans have to be so careful and only drink clean water?
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Flight of imagination
A golf ball has dimples on its surface to increase the efficiency of airflow over it and let it fly further. Why isn't the skin of aircraft and cars similarly dimpled? Would it compromise their structural integrity?
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Red leaf, yellow leaf
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Hair shadows
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Fuzzy thinking
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Thorny problem
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