At the shopping mall, you probably think about spending, not saving. Think about all the lights that keep the mall bright. Think about all the water faucets in the toilet. Think about all the air conditioning in summer. Saving energy is a hot topic for such a big place! Many things at the mall use energy. Electric lights, infrared faucets and air-conditioners need electricity to work. One way to save energy is by keeping lights clean. More and more dust and dirt make the lights less bright. When  malls keep lights clean, they can use fewer lights and keep the area just as bright ,Using fewer lights means using less energy. You step up to the  water faucet. The water starts to flow. You don't have to touch a thing. Why do malls have such fancy faucets?. The answer is simple. They save water. Sometimes people forget to turn the water off after they wash. Infrared faucets turn themselves off. The... Which of the following cannot save energy?
Using fewer lights. Using infrared faucets. Using air-conditioners Keeping lights clean.