Basically, there are three types of fatigue: physical, path ol og ic al ( 病理的 ), and psycholo g ical . A s you might suspect, each differs significantly from the others. When you exercise your body, you produce waste products . Muscles, for example, discard l a ctic acid (乳酸) into the blood ; cells dump in carbon dioxide. When these wastes reach a certain level in the blood , the brain is notified and your activity level drops. Excess wastes in the muscles may produce soreness. I f the blood of a physically fatigued animal is injected into a rested animal, it will prod uce fatigue. The solution to this type of fatigue is simple---rest. That should revive you; if it doesn’t, an other cause should be sought. Have you ever become involved in so many activities that you had to be in two places at once? This is what happens when your body has a disease. The cells are overtaxed and cannot keep up with bo t h fighting the disease and keeping you active. The result is fatigue. Some communicable diseases l ike the flu and colds are notorious for draining your energy. Other non-communicable diseases, like anemia ( 贫血 ), drain you because you are lacking an important body ingredient. Being overweight can cause patho1o g ical fatigue . It should be obvious that this type of fatigue is not going to go away without treatmen t. I n a way , patho1o g ical fatigue is a li fesaver. It lets you know something is wrong and that you need rest. Even a poor diet can produce patholog ic al fatigue. Frequently, people who go on crash diets develop patho1o g ical fa ti gue, and if the diet is not improved , they may do physical harm to their bodies . Here is the most common type of fatigue . A l most everybody experiences it now and then. Often, the cause is an emotional war you are waging with yourself or those around you. Some of these familiar factors can bring on psychological fatigue: worries, stress, lack of exercise, boredom, depression. If you know someone with psychological fatigue, would you advise him to rest? Na way! That might be fine for our other types of fatigue, but for this one, it’s deadly . If you are ever going to be able to cope with stress , depression, or worry, you need oxygen in your cells and a more optimistic attitude. Get out of the chair and do something! Believe it or not, many people throw themselves into physical labor like cleaning or carpen tr y to “de-fatigue” themse l ves. If you fin d yourself in a particularly st r essful situation that you can’t p hy sically escape, escape mentally. When fatigue continues, maybe you need to get to the root of the problem. 1. The author’s purpose of writing the passage is to A . introduce the causes of fatigue B . compare various types of fatigue C . highlight the dangers of fatigue D . substantiate the solutions to fatigue 2. Physical fatigue is usually caused by A . too many stimulants in the brain B . lack of lactic acid in the muscles C . overaccumulation of waste in the b loo d D . excess carbon dioxide discarded by cells 3. Pathological fatigue will be eliminated by A . having a good rest B . having the disease cured C . having a balance diet D . having a strong immune system 4. By saying that “pathological fatigue is a lifesaver” (Line 7, Para 3), the author points out that A . on e ’s life can be saved even if he gets serious pathological fatigue B . pathological fatigue is not so serious as to threaten one’s life C . p athological fatigue is a signal warning one of his body conditions D . when one develops a disease, pathological fatigue can help cure the disease 5. Which of the following statements is TRUE about psychological fatigue? A . Medical attention is necessary for doing away with it. B . It is more serious than the other two kinds of fatigue. C . It can be eased by doing physical exercises. D . It is caused by lack of oxygen in blood cells.