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Each year in the United States, there are approximately six million pregnancies. This means that at any one time, about 4% of women in the United States are pregnant.
There are more nerve cells in one human brain than there are stars in the Milky Way.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
IgA antibodies protect body surfaces exposed to outside foreign substances. IgG antibodies are found in all body fluids. IgM antibodies are the first type of antibody made in response to an infection. IgE antibody levels are often high in people with allergies. IgD antibodies are found in tissues lining the abdomen and chest.