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Not using spray cans is just one thing you can do. Another way to protect ozone layers is to plant trees. But the best way is to cut down on air pollution by reducing the number of cars. Well, why don't you spend your energy encouraging people to use public transportation instead? Don't worry. I am working on that too.

Are you going to buy that can of spray? Yeah, Bob, I am. Why? Because those spray cans contain CFCs which deplete the ozone layer. What is that mean? Well, many scientists think that the global warming is caused by the destruction of ozone layer. And the increasing skin cancer is due to the deduction of ozone. Spray cans cause all bad? You must be joking. No, I am serious.

You know a better way to learn about auto-repair is by studying car repair manuals. You can check them at the library instead of spending money on a class. Yeah, I can try that first. So then I think I will register for the exercise science class. I have always wanted to learn about fitness.

Tom, did you see what is being offered this summer? I am thinking about registering for a class. Yeah, I have already registered. I am taking astronomy(天文学). Hey, why don't you join me, Sally? It will be fun. Well, I prefer to take something more useful. I was considering either auto-repair or exercise science.

I hate my job. I think I need to go back to school. Good for you, Lynn. What do you want to study? Well, I can't decide between environmental science and nutritional science. Well, would you prefer to work on the environment or specialize in diet and health when you graduate? I am worried about how environmental problems affect people's health. For example, chemicals are being pumped into the river near where I live. I am sure the fish farm has been contaminated by chemicals. Sounds like environmental science is for you.

You know, I get so tired of being told not to use my car. I just saw a TV show about global warming. And this man said the people who have cars are selfish. Well, many problems have been caused by pollution from heavy traffic. Yes, but what am I supposed to do? There is only one bus a day to the city where I work. And it leaves at noon. I have to be at work early in the morning. I know how you feel, Sonia. But one thing to do about it is to live closer to where you work. What? Living in all that pollution? No, thanks.