According to this passage, which of the following is true?
When you are in a state of sub-health, you should find out the reasons and relax yourself.
When you are in a state of sub-health, you should stay at home and keep silent.
When you are in a state of sub-health, you should go to see a doctor and buy some medicine.
When you are in a state of sub-health, you should have yourself examined in foreign countries.