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Why do some flowers close up at night but others stay open?

Steve Child

Glossop, Derbyshire, UK

Is it more environmentally friendly to keep my 23-year-old petrol car or to scrap it and buy a new electric one? I drive about 8000 kilometres a year and am quite old, so my car may outlast me.

Ian Burton,

Hemel Hempstead, Hertfordshire, UK

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