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Several years ago, the mayor of Chicago, Illinois, visited Germany, a leader in green roof design.
Later he decided to have vegetation planted on Chicago City Hall. Today, the tops of many other
buildings also look like parks. In Canada, the Coast Plaza Hotel in Vancouver has a forest on its roof.
New York City has an unusual example farm for hydroponics. The farm is on a boat called the Science
Barge. Rainwater and river water are used to grow lettuce, tomatoes, cucumbers and peppers. The
farm shows the possibilities for designing rooftop systems.
Green roofs are designed to save energy and capture rainwater. Rooftops covered with plants help
keep buildings cool. They can extend the life of a roof. And they can reduce water running off into
streets and storming water systems.
Experts say green roofs usually do not get much above 27?. So temperatures might not be a problem
for growing. But rooftop gardeners have to be careful not to put too much weight on the roof. This is
true whether plants are grown in soil or water.
Earlier in 2008, researchers in Texas reported that green roofs can reduce a building's air conditioning
costs by about onefifth compared to blacktop roofs.  But they also reported that not all green roofs
perform equally well. They found that designs differ in their ability to keep buildings cool and to capture
rainwater. The researchers put experimental roofs on top of metal insulated (隔热的) boxes, to recreate
green roof conditions. The study compared products from six companies to help businesses understand
how to improve their designs. Each rooftop had sixteen different kinds of plants native to Texas. The
researchers say the presence of native plants likely helped all the green roofs capture water better
compared to sedums. Sedums are plants that need little water and often are used on green roofs. The
native plants could take in more water and release more of it to the atmosphere.
1. The author gave Paragraph 1 to ________.
A. tell us what is green roof design
B. tell us Germany is the country that leads or guides the  green roof design
C. introduce some famous hotels in the world
D. lead to the topic of the passage
2. The advantages of green roofs are mentioned in the passage  EXCEPT ________.
A. changing the local weather
B. prolonging the roof's life
C. keeping the house cool
D. reducing the house's air conditioning costs
3. According to the passage, which conclusion is WRONG?
A. Sometimes green roofs may break down the house.
B. Not all the green roofs can reduce the building's air  conditioning costs equally.
C. Different designs of green roofs have different effects on     buildings.
D. Sedums are a kind of plants native to Texas.
4. The experiment is mentioned in the last paragraph ________.
A. to find out how many different plants in Texas
B. to show us how to design green roofs
C. to introduce a kind of roof made of metal
D. to provide proofs to improve the design of green roofs

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