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
List-I | List-II |
(a) Biochemical oxygen demand | (i) Oxidising mixture |
(b) Photochemical smog | (ii) Polar stratospheric cloud |
(c) Classical smog | (iii) Organic matter in water |
(d) Ozone layer depletion | (iv) Reducing mixture |
(a) | (b) | (c) | (d) | |
1. | (i) | (iv) | (ii) | (iii) |
2. | (iii) | (iv) | (i) | (ii) |
3. | (iii) | (i) | (iv) | (ii) |
4. | (iv) | (iii) | (ii) | (i) |
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. |