Which one of the following statements is not true?
| 1. | Concentration of dissolved oxygen below 5 ppm is good for the growth of fish. |
| 2. | Clean water would have a BOD value of less than 5 ppm. |
| 3. | Oxides of sulphur, nitrogen, and carbon are the most widespread air pollutant. |
| 4. | pH of drinking water should be between 6.5-8.5. |
The major source of BOD in the river Ganga is
(1) Leaf litter
(2) Fishes
(3) Human waste
(4) Aquatic plants
B.O.D is-
| 1. | The amount of O2 utilized by organisms in the water. |
| 2. | The amount of O2 utilized by microorganisms for decomposition. |
| 3. | The total amount of O2 present in water. |
| 4. | All of the above |
Which of the following is absent in polluted water
1. Hydrilla
2. Water hyacinth
3. Larva of stone fly
4. Blue green algae
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.
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.
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. |
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 |
A student collected samples from two water bodies A and B in a metro city. The biochemical oxygen demand for 'A' is 3 ppm while for B is found to be 18 ppm. Which one of the following is true?
1. Both A and B are clean
2. Both A and B are polluted
3. A is clean but B is polluted
4. A is polluted but B is clean
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