About 20,000 years ago,much of Europe,Asia,North and South America was covered by huge sheets (片) of ice,each many kilometres thick.Since then,the ice has gradually melted and the ice sheets have retreated.Today,the only ice sheets on Earth’s land masses are found in Antarctica and Greenland.Some ice also occurs as glaciers in mountainous regions and as floating ice floes (浮冰块) in the Arctic Ocean and around Antarctica.
At first sight,these remote left-overs from the last Ice Age seem of little importance for most of us today.However,nothing could be further from the truth.Many scientists believe that our planet is warming as a result of the greenhouse gases that we are pumping into the atmosphere.If the planet becomes warmer,the ice sheets will start to melt,causing sea level to rise perhaps several metres by the end of this century.Such a rise would cause widespread flooding of low-lying coastal areas and threaten many large cities.
Observations from space suggest that parts of the major ice sheets are beginning to melt more rapidly.Meanwhile,recent satellite images have also shown that unusually large areas of sea ice have been melting during the Arctic summer.Although sea level will not be affected by the melting of the floating ice,there will be other important environmental changes.For example,ice sheets act like a mirror,reflecting sunlight and cooling Earth.If the ice disappears,Earth is likely to become warmer and major climate changes could occur.Wildlife living in the polar regions may also be destroyed.
【小题1】What does the underlined word “retreated” in Paragraph 1 probably mean?
| A．Grown. | B．Reduced. |
| C．Formed. | D．Disappeared. |
【小题2】What’s most common people’s attitude towards the ice sheets?
| A．Optimistic. | B．Critical. |
| C．Sincere. | D．Unconcerned. |
【小题3】What would happen if the greenhouse gases continue to increase?
| A．Vast amounts of land will be flooded. |
| B．Large cities in the world will disappear. |
| C．The sea level will drop to its lowest level. |
| D．Global temperatures will see ups and downs. |
【小题4】What can we infer from the last paragraph?
| A．Ice sheets melt faster than floating ice. |
| B．The melting of floating ice isn’t damaging. |
| C．Sea ice melting will have disastrous effects. |
| D．Space research contributes to climate changes. |
