"Hey, don't read in the hallway. Your eyesight will be damaged." You must have heard such warnings many times. Don't read in dim  light! This is one of the "pearls of wisdom" that are supposed to help us live a healthy life. Such common beliefs, however, lack scientific basis, according to a paper published recently in theBritish Medical Journal. Do you believe in the following everyday wisdom? Reading in dim light ruins your eyesight. In dim light, you might blink   more, feel discomfort from drying and have trouble focusing. But the majority of eye experts believe it is unlikely to do any permanent damage. We must drink at least eight glasses of water a day In 1945, the Nutrition Council in US suggested that people need to consume 2.5 litres of water a day. But the water contained in food, particularly fruit and vegetables, as well as in milk, juice and soft drinks, also counts towards the total. We only use 10 percent of our brains. This myth arose as early as 1907. People have long argued about our power of self-improvement and our brains' potential abilities. But detailed imaging shows that no area of the brain is silent or inactive. Shaving your legs causes hair to grow black faster and thicker. This theory is also illusion. Shaving has no effect on the thickness or rate of hair growth, studies say. Just over time, the edge of hair gets worn away and thus the edge of long hair becomes finer  . So hair that is newly grown gives the impression of darkness. This passage is most likely to be found in   _   ?
a newspaper a science fiction a biology textbook a medical book