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The ratio of hydrogen atoms to oxygen in water (H2O) is 2:1.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Alzheimer's disease affects only about 10% of people older than 65 years of age. Most forms of decreased mental function and dementia are caused by disuse (letting the mind get lazy).
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.