Earth Hour started in Sydney on March 31st, 2007. It calls on families and buildings to turn off the lights from 20:30 to 21:30 on the last Saturday night of March.    A year later, on March 29, Earth Hour 2008 became a global activity and was supported by 50 million people from thirty-five countries. On March 28, 2010 over 2100 cities in another eight countries took part in it.
In 2012 in China, there were many cities taking part in this activity, especially some large cities, such as Beijing, Shanghai... Many citizens(市民) consciously (有意识的) turned off lights in the hour.    In colleges some students held some activities to make all the students leave their dormitories.
It was 20:30, Beijing time.    In Shanghai some people were taking a walk with their families or friends. And in Ningbo some young people were holding a party in a park, singing and dancing.    
Earth Hour has a variety of activities, but the final goal is the same, that is focusing on (聚焦) climate change and protecting the environment for individuals.

A. The people from the three cities felt very relaxed. B. In 2007 more than 2.2 million homes and businesses turned off their lights. C. And without lights, they could also enjoy themselves. D. Some people in Beijing were having a nice talk with their friends. E. Earth Hour came to China on that day, too. F. We all believe that this activity can change the situation at present. G. Because of source, we must take measures.