Answer:
D. people
Step-by-step explanation:
Until the mid-19th century, the human race maintained relative harmony with the environment. With the emergence of the industrial age and the large urban agglomerations, there was a break in this harmony, which led to an increasing fall in the standard of living of the environment, with the death of rivers and the disappearance of green areas. This inconsequential devastation is called pollution.
Rivers are polluted by discharges from untreated urban sewage, industrial complexes, mining, etc. This type of pollution is avoided by properly treating these discharges.
Deforestation also causes rivers to die, drying up their beds.