A、They are no longer produced. B、They are used up faster than they are created. C、The growing season of their source has become

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 erergy 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 snail, 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 uo 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.
1. What is the main topic of this talk?
2. What does the speaker say about the accumulation of fossil fuels?
3. Why does the speaker refer to fossil fuels as nonrenewable?