A、On the last Saturday of March. B、On the third Saturday of March. C、On the last Sunday of March. D、On the third Sunday of March

Earth Hour is a global event organized by World Wide Fund for Nature. (29) It is held on the last Saturday of March annually, asking households and businesses to turn off their non-essential lights and other electrical appliances for one hour to raise awareness towards the need to take action on climate change.
    "Earth Hour" began in Sydney in 2007. On March 31st, 2007, 2.2 million residents of Sydney participated by turning off all non-essential lights. As an added bonus, Sydney residents joining the movement said they could see more stars than ever during that night. After that, "Earth Hour" spread around the world at an amazing speed. In 3 years, it has grown into one of the world’s largest joint actions dealing with climate change.
    Earth Hour 2009 was from 8: 30 p. m. to 9: 30 p. m. local time, March 28, 2009. (30) 88 countries and more than 4,000 cities joined Earth Hour 2009, ten times more cities than Earth Hour 2008 had. Among the participants in 2009 was, for the first time, the United Nations headquarters in New York City. The U. N. conservatively estimates that its participation will save ＄102 in energy.
    Reports show that (31) the Philippines topped the Earth Hour participation as 647 cities and towns or over 15 million Filipinos were estimated to have joined in the hour-long lights-off at 8:30 - 9:30 PM local time. (31) This was followed by Greece with 484 cities and towns participating, and Australia with 309.