Biochemical Oxygen Demand (BOD) is-

1. Amount of oxygen required by bacteria to decompose organic matter in a certain volume of a sample of water.
2. Amount of CO2 required by bacteria to decompose organic matter in a certain volume of a sample of water.
3. Amount of O3 required by bacteria to decompose organic matter in a certain volume of a sample of water.
4.  None of the above

Subtopic:  Water Pollution - Biological Oxygen Demand |
 92%
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B.O.D is connected with-

1. Organic matter

2. Microbes

3. Both (1) and (2) 

4. None of the above.

Subtopic:  Water Pollution - Biological Oxygen Demand |
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Incorrect statement among the following is: 

1. Oxides of sulphur, nitrogen, and carbon are the most widespread air pollutant.

2. pH of drinking water should be between 6.5 and 8.5.

3. Concentration of dissolved oxygen below 6 ppm is good for the growth of fish.

4. Clean water would have a BOD value of less than 5 ppm.

Subtopic:  Gaseous Pollutants - Oxides of C & N | Air Pollution - Ozone | Water Pollution - Biological Oxygen Demand |
 71%
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Biochemical oxygen Demand value less than 5 ppm indicates a water sample to be : 

1. Highly polluted.

2. Poor in dissolved oxygen.

3. Rich in dissolved oxygen.

4. Not suitable for aquatic life.

Subtopic:  Water Pollution - Biological Oxygen Demand |
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 Phytoplanktons kill the fish because :

1. Phytoplanktons decrease the BOD level that causes the death of fish.
2. Phytoplanktons increase the BOD level that causes the death of fish.
3. Phytoplanktons reduce the amount of dissolved CO2.
4. None of the above.

Subtopic:  Water Pollution - Biological Oxygen Demand |
 69%
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