Feel tired lately? Has a doctor said he can’t find anything wrong with you? Perhaps he sent you to a hospital, but all the advanced equipment there shows that there is nothing wrong with you. Then , consider this: you might be in a state of sub - health （亚健康）. Sub - health, also called the third state or gray state, is explained as a borderline state between health and disease. According to the survey by the National Health Organization, Over 45 percent of sub - healthy people are middle-aged or elderly. The percentage is even higher among people who work in management positions as well as students around exam week. Symptoms （征兆）include a shortage of energy, depression, slow reactions, insomnia （失眠）and poor memory , Other symptoms include shortness of breath, sweating and aching in the waist and legs. The key to preventing and recovering from sub - health, according to some medical experts, is to form good living habits, ale mate work and rest, exercise regularly, and take part in open air activities. As for meals, people are advised to eat less salt and sugar . They should also eat more fresh vegetables, fruits, fish because they are rich in nutritional elements - vitamins and trace elements - that are important to the body. Nutrition experts point out that it is not good to eat too much at one meal because it may cause unhealthy changes in the digestive tract （消化道）. They also say that a balanced diet is very helpful in avoiding sub - health. 小题1:When you are in a state of sub - health, you should________. A．stay home and keep silent B．go to a doctor and buy some medicine C．not consider it very serious D．find out the reasons and relax yourself 小题2:Middle - aged people may be easy to get sub - healthy because________. A．they have used up their energy B．they have lost their living hopes C．they have more pressure in life and work. D．they have changed their way of life 小题3:The key to preventing you from falling into a state of sub health is to________. A．keep on working regularly B．go to sleep a bit earlier C．form good living habits D．take medicine if necessary 小题4:As for food, experts suggested that________. A．we should never eat meat B．we should have variety of food C．we should eat less than usual D．we should have meals without sugar 小题5:The underlined word “alternate” in this passage is closest in meaning to________ A．arrange by turns B．cause to take place C．make up for D．keep away from