根据短文理解，从A、B、C、D四个选项中选择最佳答案填空。
Many scientists say that the world is getting hotter and hotter. If they are right, the ice at the North and South Pole will melt eventually. If this happens, the sea will 1 and may cover most or all of Singapore. This will force everybody to move to a 2 country.
We know that the sun 3 the earth. The heat from the sun hits the ground, and some of it goes back into the sky. However, factories and cars 4 a lot of carbon dioxide (二氧化碳). When the gas rises into the sky, the heat from the sun can come through them but the heat from the ground cannot. It 5 near us in the sky and makes the 6 hotter and hotter every year.
Scientists 7 this the “greenhouse effect” because a greenhouse is a small glass building which is hot inside. It is used for 8 plants in cool countries. Many countries are 9 about the “greenhouse effect”. They are trying to stop factories and cars from sending 10 gases into the sky. Scientists are not sure when the world will get much hotter. Some people say that the “greenhouse effect" has started already and has begun to affect (影响) the world's weather.
