Class XII

Most hazardous metal pollutant of automobile exhausts is
  1. mercury
  2. cadmium
  3. lead
  4. copper
Which one of the following organism is used as indicator of water quality
  1. Beggiatoa
  2. Chlorella
  3. Azospirillum
  4. Escherichia
Drawback of DDT as pesticide is
  1. it becomes ineffective after some time
  2. it is less effective than others
  3. it is not easily/ rapidly degraded in nature
  4. its high cost
Fish die in water bodies polluted by sewage due to
  1. pathogens
  2. clogging of gills by silt
  3. reduction in oxygen
  4. fuel smell
Green-house effect is warming due to
  1. infra-red rays reaching the earth
  2. moisture layer in atmosphere
  3. increase in temperature due to increase in carbon dioxide concentration of atmosphere
  4. ozone layer of atmosphere
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