Hint: Pollution effects are direct or indirect negative impacts of adulterants on the environment, including loss of biodiversity, risks to human health, the hindering of marine activities etc. They can also be developed by human activity, such as trash or runoff produced by factories. Pollutants damage the quality of air, water, and land.
Complete answer: Water pollution can be defined as a change in physical, chemical or biological traits of water, making it inappropriate for specified use in its natural state.
Looking at the options above:
a.Water pollution: World Health Organization (WHO) has defined water pollution as inclusion of any foreign material either from natural or other sources into a water body, thereby altering the biological qualities of water and making it unfit. The level of contamination essential to render a water body degraded is highly dependent on the type of water body. Water pollution is the most significant growing problem in most Asian countries, especially the regions near the Himalayas. This option is correct.
b.Soil pollution is the degradation of land caused by the presence of human-made chemicals or other changes in the natural soil environment. It is generally influenced by industrial activity, agricultural chemicals or inappropriate disposal of waste. This option is incorrect.
c. Air pollution is a combination of solid particles and gases in the air. Ozone is a primary part of air pollution in cities. When ozone forms air pollution, it's also called smog. This option is incorrect.
d. This option stands irrelevant.
Hence, the correct answer is option a.
Note: One of the significant steps launched by the government to reduce river pollution is the National River Conservation Plan (NRCP). It is a national programme targeting the domestic pollution that goes into the surface water. It was undertaken in 1985, when NRCP began its work with the Ganga Action Plan.