Which of the following is major source of water pollution?        

Untreated sewage when disposed of in water bodies results in severe water pollution. The effect is detrimental both for aquatic life as well as for human beings.
Sewage contains all forms of waste from point sources like industries & factories, agricultural lands, domestic wastes, pathologies, hospitals, malls, schools, etc. It is laden with all types of organic and inorganic wastes.

Thus, sewage is the major source of water pollution.