Explain the following terms :

(a) Smog

(b) Pollutants

(c) CFC

(d) Eutrophication

(a) Smog — The term 'smog' is derived from 'smoke + fog' as it is formed due to mixing of smoke and fog. Smog is common in industrial areas in winters. It reduces visibility and is unhealthy for humans, animals and plants.

(b) Pollutants — The substances or materials that cause pollution are called pollutants. They are harmful for the environment and living beings. They can be natural such as volcanic ash or man-made like plastic.

(c) CFC — CFC or Chlorofluorocarbons are the synthetic chemical compounds which are used as refrigerant or cooling agent in AC and refrigerators. When these chemicals are released in atmosphere, they split due to ultraviolet rays and damage the ozone layer.

(d) Eutrophication — The process by which the excess phosphates and nitrates lead to over growth of algae and other aquatic plants in a water body, depleting the oxygen of water, is called Eutrophication.