human
Question: 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 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 from good liwing habits,alternate work and rest,exercise regularly,and take park 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. It may be easy for middle-aged people to get sub-healthy because   _  .

Choices:
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
gpt
The correct answer is 2: they have more pressure in life and work.