We humans live in different parts of the world, but we have the same "mother". She gives us everything we need in our daily life. She is our Mother Earth. April 22 is Earth Day. The theme of this year is "Green Cities". A green city is a healthy and pleasant place for people to live, according to the United Nations. A green city can get its energy from renewable   sources like solar   and wind power. Also, it is connected by clean public transportation. Moreover, a green city is made up of facilities   that can save energy and reduce waste. Around the world, many cities and countries have done well to build themselves in a green way. Chicago is well known for its green roof   program. These roofs are covered with plants. The plants get a great amount of rainwater. Later, the water evaporates   to help make the air cool and clean. So far, there are about 360 green roofs in Chicago, according to the US Environmental Protection Agency. Curitiba, Brazil, has great transportation. It opened the world's first bus rapid transit (BRT) system in 1974. BRT runs on special lanes. This makes sure that buses are on time even in traffic jams. With the help of BRT, the city has the lowest level of air pollution in Brazil. Today, many other countries have copied BRT, including China and Mexico. Singapore is home to the first zero-energy building in Southeast Asia. Zero energy means a building is able to create more energy than it uses. Zero-energy buildings work with solar panels   mainly on roofs. These panels can make electricity which powers the buildings. By 2030, Singapore plans to build 80 percent of its buildings like this. From the passage, we learn that in the three cities   _  .
people are encouraged to grow plants on their roofs special lanes are designed to solve traffic jams people make good use of solar and wind energy people are provided with a pleasant place to live