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Driving in summer, I can cool my car by using air conditioning or opening the windows. One drains the battery, the other makes the car less aerodynamic. Which is more efficient?
Penny Jackson,
Barrow-in-Furness, Cumbria, UK
Roman Zaiets/Shutterstock
Humans can’t hear ultrasound, but can it damage our hearing?
Peter White,
Cardiff, UK
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