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Giardia is one of the most common intestinal parasites worldwide, and infects up to 20% of the world population, mostly in poorer countries with inadequate sanitation. Infections are most common in children, though chronic Giardia is more common in adults.
Pubic lice (crabs) are usually spread through sexual contact. You cannot catch them by using a public toilet.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
Certain chemicals, after ingestion, can be converted by the body into cyanide. Most of these chemicals have been removed from the market, but some old nail polish remover, solvents, and plastics manufacturing solutions can contain these substances.
It is difficult to obtain enough calcium without consuming milk or other dairy foods.
![The stages of labor and delivery. (A) During the dilation stage the cervix thins and dilates to 10 c](https://biology-forums.com/gallery/47/medium_14755_28_08_12_1_52_24_82561428.jpeg)
![Position of the lungs within the thoracic cavity; anterior view illustrating regions of the lungs an](https://biology-forums.com/gallery/47/medium_14755_10_09_12_7_13_31_84901393.jpeg)