题目内容：

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 community, 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 communities.

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.

1.The underlined word “no-brainer” in Para. 1 probably means something that ______.

A．is hard to deal with                      B．is very easy

C．is of no real value                       D．deserves more attention

2.From Paragraphs 3 and 4, we can learn _______.

A．how to set up a water harvesting system      B．how a rain barrel system works

C．some advice on saving tap water            D．the benefits of using rainwater

3.What is the topic of the passage ?

A．Basic gardening skills.                    B．Water-saving techniques.

C．Wastewater treatment systems.            D．Roof rainwater collection.