题目

命题：“至少有一个点在函数的图像上”的否定是（   ）A．至少有一个点在函数的图像上  B．至少有一个点不在函数的图像上C．所有点都在函数的图像上      D．所有点都不在函数的图像上 答案：DThere is no doubt 1.        the earth is becoming warmer but there is fierce debate over whether it is human activity that has caused this global warming or whether it is just a natural phenomenon.Many scientists like Dr Janice Foster believe that people have caused the increase in the earth's temperature 2.        burning of fossil fuels like coal,natural gas and oil to produce energy 3.        byproducts are called "greenhouse" gases,the most important one 4.        carbon dioxide. These gases trap heat from the sun and therefore warm the earth,without which the earth 5.        (be) about thirtythree degrees Celsius cooler than it is. But increased amount of carbon dioxide means that 6.        (much) heat energy is trapped in the atmosphere,7.        (cause) the global temperature to go 8.       .On 9.       other hand,scientists like George Hambley believe that any warming will be mild with few bad 10.        (environment) consequences and more carbon dioxide is actually a positive thing.