Feel tired lately? Has a doctor said he can't find anything wrong with you? Perhaps he has 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. Sub-health, also called the third state or gray state, is explained as a borderline state between health and disease
According to the investigation 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(症状) include a lack of energy, depression, slow reactions, insomnia, anger, 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, alternate 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 other 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. They also say that a balanced diet is very helpful in avoiding sub-health
68. When you are in a state of sub-health, you should_______. 
A. stay at home and have a good rest.      
B. go to see a doctor and buy some medicine
C. have yourself examined with advanced equipment
D. find out the reasons and relax yourself
69. It may be easy for middle-aged people 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 begin to get older
70. We can know form the passage if you____, you can avoid falling into a state of
sub-health.         
A. eat more fresh vegetables and fruits     B. develop good living habits
C. sleep more                          D. take more medicine
71. The underlined word "alternate" in this passage is closest in meaning to ____
A. keep oneself busy with              B. cause to take place       
C. arrange by turns                      D. get rid of