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Author Question: Define what is meant by a threat to internal validity. (Read 40 times) |
In 1844, Charles Goodyear obtained the first patent for a rubber condom.
Looking at the sun may not only cause headache and distort your vision temporarily, but it can also cause permanent eye damage. Any exposure to sunlight adds to the cumulative effects of ultraviolet (UV) radiation on your eyes. UV exposure has been linked to eye disorders such as macular degeneration, solar retinitis, and corneal dystrophies.
About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.
Tobacco depletes the body of vitamins A, C, and E, which can result in any of the following: dry hair, dry skin, dry eyes, poor growth, night blindness, abscesses, insomnia, fatigue, reproductive system problems, sinusitis, pneumonia, frequent respiratory problems, skin disorders, weight loss, rickets, osteomalacia, nervousness, muscle spasms, leg cramps, extremity numbness, bone malformations, decayed teeth, difficulty in walking, irritability, restlessness, profuse sweating, increased uric acid (gout), joint damage, damaged red blood cells, destruction of nerves, infertility, miscarriage, and many types of cancer.
Approximately 15–25% of recognized pregnancies end in miscarriage. However, many miscarriages often occur before a woman even knows she is pregnant.