Câu hỏi:

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 31 to 35.

Many products such as paper, cardboards, and cups come from trees. In fact, trees are our natural assets, you can conserve trees by recycling the paper products, we can minimize the number of trees cut down a year. This is one form of waste recycling. One should understand and know the importance of recycling waste materials. One simple benefit of recycling is it saves our resources. It will be wise to reuse metal items as metal reserves may be depleting. You can hold your worn-out metal items for recycling. As mentioned earlier, recycling of waste papers can save our forests. Recycling waste not only saves our natural resources but also helps save energy. By simply recycling an item or making a basic fix to it, we can save all the energy that would have been consumed in the process of making it. The same example can be taken with plastic items. A large amount of energy can be saved by simply reusing the plastic items. To recycle waste is to simply reduce pollution. By recycling plastic material, we can reduce air pollution as well as water pollution. Plastic factories produced large amount of smoke when producing plastic material at the same time if we don't have proper waste disposal system, those waste emissions will cause water pollution. Recycling waste in a way helps reduce pollution. 

The passage mainly discusses ____.