| 21. | The temperature scale that sets freezing of pure water at 32o F:- |
| a. | Kelvin |
| b. | Fahrenheit |
| c. | Celsius |
| d. | British |
| 22. | The pollutant that causes hole in the ozone layer is- |
| a. | SF6 |
| b. | nitrousoxide |
| c. | CFCs |
| d. | PFCs |
| 23. | Ozone depletion is mostly caused by- |
| a. | |
| b. | CCL |
| c. | |
| d. | CO |
| 24. | Which one of the following is the correct percentage of the two green house gases that contribute to the total global warming? |
| a. | |
| b. | |
| c. | |
| d. |
| 25. | Pick out the potent green house gas- |
| a. | CO2 |
| b. | N2O |
| c. | CH4 |
| d. | O3 |
| 26. | Although the polar regions radiate away more heat energy than they receive by insolation in the course of a year, they are prevented from becoming progressively colder each year by the: |
| a. | |
| b. | |
| c. | |
| d. |
| 27. | The intermediate developmental stages in the ecological succession is called- |
| a. | sere |
| b. | |
| c. | |
| d. |
| 28. | The final stable community in an ecological succession is called the- |
| a. | |
| b. | |
| c. | |
| d. |
| 29. | Typically, water vapour occupies about what percentage of the air’s volume near the earth’s surface? |
| a. | |
| b. | |
| c. | |
| d. |
| 30. | Heavy dust can cause- |
| a. | |
| b. | |
| c. | |
| d. |
