What Scientific Instrument Enhances the Quality of Life for People Around the World?

 
Eva, one of our own graduate students, asks this question on her blog easternblot [Quality of Life]. It's a multiple choice question. How hard can it be?

I mean, there can't be all that many scientific instruments that enhance the quality of life for people all around the world, right? Before checking her list, see if you can think of a few possibilities.

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