Chinese artists perform on stage during the opening ceremony of the International Horticultural Exposition 2011 at the Exposition Park on April 28, 2011 in Xi'an, Shaanxi Province of China. The World Horticultural Exposition 2011 will be held in Xi'an from April 28 to October 22. (Photo by ChinaFotoPress/Getty Images)

A runner traverses the route during the Mount Everest Challenge Marathon which winds past spectacular views of Everest and Kanchenjunga at Sandakphu National Park in the month of November 1995 near Darjeeling, India.

Three secondary schoolboys smoking an illicit cigarette in Hyde Park, London. (Photo by Evening Standard/Getty Images). May 1972

A lesser or red panda stands on its hind legs at Chiba Zoological Park on May 20, 2005 in Chiba, Japan. The panda can maintain the position for over 10-20 seconds at a time. (Photo by Koichi Kamoshida/Getty Images)

Impala pictured in the Kruger National Park on December 7, 2007 in Mpumalanga, South Africa. (Photo by Warren Little/Getty Images)

Sydney artist Phillip George poses with two surfboards of his own design at Marks Park, Tamarama on December 16, 2008 in Sydney, Australia. (Photo by Don Arnold/Getty Images)

A student shouts slogans against Venezuelan President Nicola Maduro during a protest on the main highway in Caracas on March 30, 2017. Venezuela' s Supreme Court took over legislative powers Wednesday from the opposition- majority National Assembly, whose speaker accused leftist President Nicolas Maduro of staging a “coup”. (Photo by Juan Barreto/AFP Photo)