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.

             In the world today, particularly in the two most industrialized areas, North America and Europe, recycling is big news. People are talking about it, practicing it, and discovering new ways to be sensitive to the environment. Recycling means finding ways to use products a second time. The motto of the recycling movement is "Reduce, Reuse, Recycle".
            The first step is to reduce garbage. In stores, a shopper has to buy products in blister packs, boxes and expensive plastic wrappings. A hamburger from a fast food restaurant comes in lots of packaging: usually paper, a box, and a bag. All that packaging is wasted resources. People should try to buy things that are wrapped simply, and to reuse cups and utensils. Another way to reduce waste is to buy high-quality products. When low quality appliances break, many customers throw them away and buy new ones - a loss of more resources and more energy. For example, if a customer buys a high-quality appliance that can be easily repaired, the manufacturer receives an important message. In the same way, if a customer chooses a product with less packaging, that customer sends an important message to the manufacturers. To reduce garbage, the throwaway must stop.
            The second step is to reuse. It is better to buy juices and soft drinks in returnable bottles. After customers empty the bottles, they return them to the store. The manufacturers of the drinks collect the bottles, wash them, and then fill them again. The energy that is necessary to make new bottles is saved. In some parts of the world, returning bottles for money is a common practice. In those places, the garbage dumps have relatively little glass and plastic from throwaway bottles.
           The third step is being environmentally sensitive is to recycle. Spent motor oil can be cleaned and used again. Aluminum cans are expensive to make. It takes the same amount of energy to make one aluminum can as it does to run a color TV set for three hours. When people collect and recycle aluminum (for new cans), they help save one of the world's precious resources.

The garbage dumps in some areas have relatively little glass and plastic because_____.

It gets ______ to understand what the professor has explained. more difficult than