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(a) Greenhouse gases trap heat in the atmosphere, which makes the Earth warmer. Carno dioxide, methane are generally called greenhouse gases. These gases absorb long wave (infrared) radiation radiated from the earth. Theses gases radiate heat energy a major part of which again comes to Earth’s surface, thus heating it up. They prevent heat from escaping to outer space, so are functionally comparable to glass panels of a greenhouse and are called greenhouse gases  

(b) Catalytic converter is a device that uses a catalyst to convert the harmful compounds in car exhaust into harmless compounds. They are fitted into the automobiles and have expensive metals namely platinum-palladium and rhodium as the catalysts. As the exhaust passes through the catalytic converter, unburnt hydrocarbons are converted into carbon dioxide and water and carbon monoxide and nitric oxide are changed to carbon dioxide and nitrogen gas, respectively. 

(c) Ultraviolet-B radiations. These are high energetic UV-radiations which are mostly blocked by the ozone layer. UV-B damages DNA  and causes mutations in it. UV-B radiation is very harmful for eyes. It leads to aging of skin and causes skin cancers. When cornea absorbs UV-B, it leads to the inflammation of cornea and may cause diseases like snow blindness cataract. Exposure may even permanently damage cornea.