[单项选择]Scientists say that something very serious is happening to the earth. It will begin to get __56__ in the following years. There will be major changes in ___57__ in the new century. Coastal waters will have a __58__ temperature. This will have a __59__ effect on agriculture. In northern areas, the __60__ season will be ten days longer by the year 2010. However, in warmer areas, it will be too dry. The __61__ of water could __62__ by eighty percent. This would __63__ a large decrease in agriculture production. 　　World temperature could __64__ two degrees centigrade by the year 2040. However, the increase could be three times as great in the Artic and Antarctic area. This could cause the __65__ sheets to melt and raise the __66__ of the oceans __67__ one to two meters. Many coastal cities would be __68__ water. 　　Why is this happening There is too __69__ carbon dioxide in the air. __70__ oil, gas and coal burn, they create large amounts of carbon dioxide. This carbon dioxide lets
A. If
B. Because
C. When
D. Why

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