Today I‟d like to begin a discussion on the problem of heating up of the earth. First we‟ll touch on the relationship between fluorocarbons and the ozone layer. You probably remember that the ozone layer is the protective shield around the earth. It is important to all life, because it filters out harmful ultraviolet light from the sun. Ozone itself, a form of oxygen, is regularly destroyed by natural chemical processes. The problem now is that too much of the ozone layer is being destroyed. Scientists suspect that certain chemicals, such as fluorocarbons, are contributing to the depletion of the ozone layer. And How do we use fluorocarbons? The most common users are in spray cans and cooling systems. The chemical pollution from these fluorocarbons can account for some of the ozone losses that have been reported. There are, however, new studies linking the sun itself to the depletion of the ozone layer. We‟ll go into that new study more next time. 28. Who is the most likely speaker? A. A doctor B. A mechanic C. A professor D. A chemist 9. What is the speaker’s main topic? A. Ultraviolet B. The use of spray cans C. Air-conditioning systems D. Fluorocarbons and the ozone layer 30. What is the most important purpose of the ozone layer? A. Providing fluorocarbons B. Shielding the sun C. Protecting the earth D. Destroying chemicals 31. What is the ozone layer made of? A. Fluorocarbons B. Oxygen C. Shields D. Ultraviolet 32. What will the speaker probably discuss next? A. How to make air conditioner and fluorocarbons. B. Harmful effects of ultraviolet light C. The make-up of the ozone layer D. The sun as a cause of ozone layer depletion