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Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
Blood is approximately twice as thick as water because of the cells and other components found in it.
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.
The B-complex vitamins and vitamin C are not stored in the body and must be replaced each day.
The modern decimal position system was the invention of the Hindus (around 800 AD), involving the placing of numerals to indicate their value (units, tens, hundreds, and so on).