Besides containing attractive flowers, trees and other plants that beautify the communit

y, eco-friendly rain gardens are healthy for the environment and the people living and working nearby.

A rain garden is not very different from a traditional garden. It is just a far more eco-friendly garden. Usually it is built lower than the ground. Rain gardens make smart use of rain and storm water by temporarily holding water from rain and storms and letting it soak(渗透) slowly into the ground before it runs into streams or enters the public drinking water supply.

Thus, a rain garden keeps the water，allowing it to be used as needed by plants in the rain garden, rather than flowing immediately into nearby streams and going unused. The water will soak slowly into the ground within a day or two. This creates an advantage that the rain garden does not allow mosquitoes to breed. This is a simple, attractive, and eco-friendly “green” way to treat storm water.

What’s more, planting a rain garden helps reduce pollution and improve the environment. Without using expensive machinery and chemicals, rain gardens remove harmful chemicals in the rainwater and cut down on the amount of pollution reaching streams and rivers by up to 30%.

Native plants are recommended for rain gardens because they are more used to the local climate, soil, and water conditions. They may attract local wildlife such as native birds. Water your rain garden immediately after planting and once a week, unless you have had at least an inch of rain during the week. Once native plants establish the necessary root system，they will require little care.

Often，local governments and private businesses develop large rain gardens in their yards and in public parks as a way to improve the environment and solve flooding problems. However, you don’t need to be a professionally environmental engineer to create a rain garden. As long as you’re eco­conscious homeowners，you can help the environment by building smaller rain gardens in your yards.

B-21.Which of the following is NOT true for the function of rain gardens？

A、They are good for living conditions.

B、They increase pollution.

C、They can beautify the community.

D、They improve the environment.

22阅读B-21题干中Passage Two材料，完成本题。

B-22. Which of the following is the eco-friendly function of rain gardens discussed in Paragraph 4？

A、They can help reduce the pollution problem.

B、They can keep the rain and storm water.

C、They can be healthy for the people around.

D、They can make the environment more beautiful.