Explain giving reasons
a) Balanced diet is necessary for maintaining healthy body.
b) Health of an organism depends upon the surrounding environmental conditions.
c) Our surrounding area should be free of stagnant water.
d) Social harmony and good economic conditions are necessary for good health.

Explanation

(a) Balanced diet provides necessary raw materials (carbohydrates, proteins, fats, minerals and vitamins etc.) and energy in appropriate amounts for the proper growth and functioning of the healthy body.
(b) Literally speaking, health is a state of well being. It is a state of complete physical, mental and social well being and depends upon the surrounding environmental conditions. If the surroundings are unhygeinic, one is likely to get infection or disease.
(c) Stagnant ~ater, in the surrounding area where we live, provides breeding site for many insect vectors (e.g., mosquitoes). These vectors flourish in stagnant water and cause many diseases in human beings. (d) Social harmony and good economic conditions are also necessary for good health. Job opportunities have to be available in the society where we live. Proper earning is necessary to get balanced diet for everyone in the family.
Similarly, social equality and harmony involves participation in one another's joys and sorrows, helping each other at the time of need etc.