Eight years ago, officials in Chicago, Illinois, decided to replace the black roof on the city government building with a planted garden. The aim was to reduce energy costs, improve air quality and control the rainwater entering the city’s waste system（系统）．Green roofs also help reduce a problem called urban heat islands（城市热岛现象）．During hot weather, the building’s root could reach temperatures of up to 76℃. With the garden, the temperature of the root area was reduced by at least 30℃. Workers planted over 150 kinds of plants that could stand bad weather. Now the area is cooler, the building requires less energy to keep cool, and the roof looks nice. Chicago also offers money to help people pay for building their own green roots.

　　About five years ago, officials in Thane, India, decided to reduce the city’s depending on power from coal. The city often experiences lack of power because of the large numbers of people using electricity. Officials decided to save energy by putting water heaters（热水器）powered by the sun on top of the city’s main hospital. The hospital saved thousands of dollars in energy costs each year. Officials then began building this kind of water heater around the city.

　　China has announced plans to build a city called Dongtan. The company designing the city says it will produce its energy from the wind, sun and waste. The aim is for the city to be an example to the rest of China.

What did the officials in Chicago decide to do?（　　）

• A.To grow plants on the roof of the government building
• B.To make use of the rainwater in the city’s waste system
• C.To improve the air quality of the city greatly
• D.To build another government building