US President Barack Obama greets volunteers before planting Earth Day trees at Kenilworth Aquatic Gardens in Washington, April 21, 2009. [China Daily/Agencies]
![US President Barack Obama greets volunteers before planting Earth Day trees at Kenilworth Aquatic Gardens in Washington, April 21, 2009. [China Daily/Agencies]](http://images.china.cn/attachement/jpg/site1007/20090422/000bcdb95f1d0b58f6eb1f.jpg "US President Barack Obama greets volunteers before planting Earth Day trees at Kenilworth Aquatic Gardens in Washington, April 21, 2009. [China Daily/Agencies]")