Physical fitness refers to good health, and is the result of regular exercise, proper diet and nutrition, and proper rest for physical recovery. A person who is physically fit will be able to walk or run without getting breathless and he or she will be able to carry out the activities of everyday living and will not need help. How much each person can do will depend on their age and whether they are a man or woman. A physically fit person usually has a normal weight for height. The relation between height and weight is called the Body Mass Index. A taller person can be heavier and still be fit. If a person is too heavy or too thin for the height it may affect the health.  Mental health refers to a person's emotional and psychological well-being. "A state of emotional and psychological well-being in which an individual is able to use his or her thinking and emotional(feeling) abilities, function in society, and meet the ordinary demands of everyday life." One way to think about mental health is by looking at how well a person functions. Feeling capable and efficient, being able to handle normal levels of stress, having good friends and family, and leading an independent life, and being able to "bounce back" or recovering from hardships, are all signs of mental health. Public Health refers to trying to stop a disease that is unhealthy to the community, and does not help in long life or promote your health. This is fixed by organized efforts and choices of society, public and private clubs, communities and individuals. It is about the health of many people, or everybody, rather than one person. Public health stops instead of encouraging a disease through surveillance  of cases. To prevent being sick, it is good to do healthy behaviors, such as hand washing, vaccination programs and so on. When infectious diseases break out, washing hands may be especially important. Once Bird Flu takes place, that refers to   _  .
the problem of public health the problem of mental health the problem of physical health the importance of washing hands.