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Vaccines prevent between 2.5 and 4 million deaths every year.
Thyroid conditions may make getting pregnant impossible.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Cucumber slices relieve headaches by tightening blood vessels, reducing blood flow to the area, and relieving pressure.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
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