i-16-1.txt

很好用哦

(man) Today I want to discuss fossil fuels such as coat, oil, and natural gas. The term "fossil fuel" refers to the trapped remains of plants and animals in sedimentary rock. You see, living plants trap energy from the sun by the process of photosynthesis, and they store the energy in their chemical compounds. Most of that energy is released when the plant dies and decays. However, sometimes organic matter is buried before it decays completely. In this way some of the solar energy becomes trapped in rocks --- hence the name fossil fuel. Although the amount of organic matter trapped in any one growing season is small, the accumulated remains from millions of years are considerable. Because the accumulation rate is so slow --- millions of times slower than the rate at which we now dig up this organic matter and burn it for energy --- we must consider fossil fuels as nonrenewable resources. Tomorrow we'll be discussing alternatives to fossil fuels that can be renewed.