题目内容：

课文语法回顾

All scientists subscribe to the view that the increase in the earth’s temperature is due to the burning of fossil fuels like coal, natural gas and oil to produce energy. Some byproducts of this process1. (call) “greenhouse” gases, and the most important one of2.is carbon dioxide. Dr. Janice Foster explained “There is a natural phenomenon3.is called the greenhouse effect. This is when small amounts of gases in the atmosphere, like carbon dioxide, methane and water vapour trap heat from the sun and therefore warm the earth. 4.for the greenhouse effect, the earth would be about 33 degrees Celsius cooler  than it is. So, we need those gases. The problem begins when we add huge quantities of extra carbon dioxide into the atmosphere. It means that more heat energy tends to be trapped in the atmosphere 5. (cause) the global temperature to go up.