A、Middle-aged and elderly people. B、Young working mothers. C、University students and teachers. D、Children and adolescents. A

Feeling stressed lately? Has the doctor said he cannot find anything wrong with you? Perhaps he sent you to a hospital, but all the fancy equipment there showed that there was 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 defined as a borderline state between health and disease.
    According to an 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-time, due to their heightened exposure to stress.
    The key to preventing and recovering from sub-health, according to some medical experts, is to form good living habits, alternate work with rest, exercise regularly, and take part in open air activities.
    As for meals, people are advised to eat less salt and sugar. They should eat more fresh vegetables, fruits, fish and aquatic products because they are rich in nutritional elements—vitamins and trace elements—that are indispensable 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.