For most of us, the rain that falls on our roof runs off into the ground or the sewer(下水道)

For most of us, the rain that falls on our roof runs off into the ground or the sewer(下水道) system. But if you want to save a little water and reuse it on your lawns or plants --- or even use it for laundry, dishes, or other needs --- collecting rainwater from your gutter’s downspouts(檐槽的水落管) is a no-brainer.
According to John C. Davis, writing in E / The Environmental Magazine, just about any homeowner can collect rainwater, given that the roof and gutters do most of the work. And since an inch of rain falling on a 2,000-square-foot roof produces some 1,200 gallons of water, you can harvest enough to water your lawn or garden.
Plants and grass actually do better when fed rainwater instead of tap water, which is usually treated with substances that can hold back plant growth. Using rainwater can also extend the life of pipes, since the salts added to tap water may gradually damage the pipes. However, homeowners should set up a water purification system if they do plan to use rainwater for inside needs.
Rainwater harvesting can also be good for the local munity, as it reduces the erosion, flooding, and pollution associated with heavy rainfall, and reduces dependence on public water supplies. So some states fund rainwater collection systems in their local munities.
Many varieties of rain barrel(桶) systems, starting at just $100, are available for home use. A typical setup is simply a rain barrel positioned under a gutter’s downspout. Skillful homeowners can make their own water harvesting systems, but buying one is a lot easier. Most garden centres offer a range of choices as well as tips.
【小题1】The underlined word “no-brainer” in Para. 1 probably means something that     .A．is hard to deal withB．is very easyC．is of no real valueD．deserves more attention【小题2】From Paragraphs 3 and 4, we can learn     .A．how to set up a water harvesting systemB．how a rain barrel system worksC．some advice on saving tap waterD．the benefits of using rainwater【小题3】What is the topic of the passage ?A．Basic gardening skills.B．Water-saving techniques.C．Wastewater treatment systems.D．Roof rainwater collection.B