Give any four factors necessary for a healthy person.

(1) Environment. (i) A clean physical environment with the help of public health services. (ii) A congenial social environment.

(2) Personal hygiene. Personal cleanliness prevents catching up of infectious diseases and resistance against it.

(3) Nourishment. Intake of a proper balanced diet keeps the immune system strong.

(4) Vaccination. Timely vaccination against major disease (e.g. polio, T.B., chicken pox, etc.) protects oneself from catching those diseases.