单选题
The establishment of Earth Day began with an idea proposed in October 1969 by John McConnell, a San Francisco resident. McConnell approached the San Francisco Board of Supervisors with a resolution to devote one day a year to public awareness dedicated to nature and the weak ecosystem that makes up it. The day's events would emphasize the urgency of all inhabitants of the planet to take responsibility for building a healthy and ecologically sustainable planet for the present and long into the future. The board was impressed with McConnell's idea and declared Earth Day an annual celebration to be held on March 21, the date of the vernal equinox. McConnell stated "This is the moment when night and day are equal throughout the earth — reminding us of Earth's beautiful systems of balance which humanity has partially upset and must restore." Earth Day was established as a national day of celebration in the United States in 1970 and was embraced by the United Nations in 1971 when it declared an Earth Day ceremony to be held each year on the day of the March Equinox. When the first Earth Day was celebrated in the United States on April 22, 1970, twenty million participants nationwide took part in teach-ins, street demonstrations, and workshops in 2,000 communities and 12, 000 college and high school campuses. The major public concern at that time was industrial pollution and its effect on the air we breathe, the water we drink, and the health of the planet we live in. Those celebrations led to powerful public outcries for legislation mandating ecologically sound environmental policies and rigid controls on industrial pollution. Over the years, the issues of concern have expanded greatly into all aspects of air, water, soil, and noise pollution. Whether it comes from vehicles, factories, agriculture, housing, or private property, public concern and activism continue with citizens from around the world involved in efforts to achieve a sustainable and enduring ecosystem. Earth Day activities are supported and sponsored by a large network of organizations, government agencies, businesses, universities, and institutions. They work diligently each year to make Earth day events meaningful and relevant to the inhabitants of Planet Earth. The regular observance of this holiday fixes environmental values into the national consciousness and provides an opportunity to introduce environmental issues into schools, media and public events. It should be noted that Earth Day activities have been instrumental in bringing about many of the significant environmental changes that have taken place in the last three decades.