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Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Vaccines prevent between 2.5 and 4 million deaths every year.
Thyroid conditions may make getting pregnant impossible.
The horizontal fraction bar was introduced by the Arabs.
Asthma is the most common chronic childhood disease in the world. Most children who develop asthma have symptoms before they are 5 years old.
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