This combination of April 15, 2013 and April 2, 2014 photos show a police officer clearing Boylston Street following a bomb blast near the finish line of the 2013 Boston Marathon, and pedestrians crossing at the same corner nearly a year later in Boston. (Photo by Charles Krupa/AP Photo)

Chile's Javier Campillay drives past the burning car of Kazakhstan's Bauyrzhan Issabayev and Gabdulla Ashimov during the Dakar Rally 2014 Stage 2 from San Luis to San Rafael, on January 6, 2014. (Photo by Jean-Paul Pelissier/AFP Photo)

British-based Ukrainians gather outside the Russian Embassy in London to protest against the build-up of troops in the Crimea region, on March 2, 2014. The demonstrators chanted and held banners demanding “Hands off Ukraine”. (Photo by John Stillwell/PA Wire)

Italian movie star Gina Lollobrigida shows a 0.95 super-grand-angle lens mount on a 35mm camera, as she presents her collection of photographic equipment at her home on the ancient Appian Way on the outskirts of Rome, July 2, 1964. (Photo by Girolamo di Majo/AP Photo)

A man sledges on Primrose Hill with his daughter and their dog on February 5, 2012 in London, England. The United Kingdom is experiencing heavy snowfall with many areas affected. (Photo by Peter Macdiarmid/Getty Images)

"La Montagna di Sale (The Salt Mountain)" by Mimmo Paladino is displayed in Piazza Duomo on April 5, 2011 in Milan, Italy.

Afghan police recruits undergo training at the Afghan Police Academy October 5, 2010 in Kabul, Afghanistan. (Photo by Majid Saeedi/Getty Images)

A pair of giant pandas play in their enclosure at the Beijing Zoo on June 5, 2012 in Beijing, China. With an estimated 1,600 living in the wild, the endangered giant panda dwell in a few mountain ranges in central China, in Sichuan, Shaanxi, and Gansu provinces. (Photo by Lintao Zhang)