The latest meaning of health is whether health is the normal state of human life.

A, disease-free is not real health, it's just physical health, A is wrong.

B, health is not only physical health, mental health, but also a good state to adapt to society. B wrong.

C, the World Health Organization put forward that "health is not only the absence of disease, but also a good state of physical, psychological and social adaptation", and C is correct.

So choose: C.