1. Steam engine. This one came first and led to other engines. No airplanes, no cars, no boats, without engines.
2. Computer. No IW, without a cpu.
3. Vaccine. Nearly wiped out several diseases. Polio, Malaria, etc...
4. Telephone. Can you visit a friend who lives in a different country everyday? No.
5. Lightbulb. Flammable lanterns, and unreliable candles? I think not.
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Everyone is entitled to their own opinion, I just don't have to listen.
