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I don't there's any that does not involve using more advanced technologies. Note that 100 years ago we were burning coal in every home, towns were full of smog, many towns even had no sewage and people lived for 30 years on average.
I don't there's any that does not involve using more advanced technologies. Note that 100 years ago we were burning coal in every home, towns were full of smog, many towns even had no sewage and people lived for 30 years on average.