题目内容：

Green Roofs （屋顶）

Why would anyone want to plant a garden on a roof? People are finding out that it is good for the environment and good for them.

Cities can be as much as four to ten degrees warmer than the countryside. Green rooftops can help cool the air in cities. One green roof will not do much to change the temperature of a city. However, when more buildings begin to convert their rooftops to green spaces, it can make a real difference. Buildings that are cooler also use air conditioning less often. This reduces the amount of energy a building uses.

Cities are usually more polluted than other areas. The plants on the rooftops can even help clean the air. Gardens in the city can also provide a place for birds and bugs to live.

One unusual rooftop garden is on the rooftop of Children's Hospital in Missouri. The garden covers an area of 7,500 square feet. It is a place for the children and parents to relax and be close to nature without leaving the hospital. The garden has flowers, fountains（喷泉）, and even a goldfish pond.

Another interesting garden is on the rooftop of the Royal York Hotel in Canada. The hotel's cooks can pick herbs（草本植物）they use fresh from the roof. Some other hotels and restaurants have rooftop gardens to grow plants. They just need gardeners to care for them. Rooftop gardens can dry out quickly in the summer sun, and vegetables need frequent watering.

Not all buildings have green rooftops. For one thing, green rooftops can be more expensive than traditional rooftops. Also, a roof needs to be flat and strong enough to support the weight of the garden.

In the past, not many people knew about rooftop gardens and how good they could be for the environment. But it is changing. You may want to keep your eyes on the skies when you walk the streets in your town or city. You never know when you might catch a look of a secret garden many feet above the ground.

1.The word "convert" in Paragraph 2 probably means“         ” .

A.connect B.move C.change D.take

2.The sixth paragraph is mainly about             .

A.why it is difficult to have green rooftops

B.when all buildings can have green rooftops

C.what buildings need to have green rooftops

D.how to make all buildings have green rooftops

3.What can we learn from the passage?

A.Cooks of hotels and restaurants care for plants in rooftop gardens.

B.Rooftop gardens in hospitals should be larger and more beautiful.

C.Rooftop gardens help people save a lot of money.

D.More and more people begin to know rooftop gardens.