Britain's Prince William and his wife Catherine the Duchess of Cambridge stand in front of Uluru in the Northern Territory of Australia April 22, 2014 (Photo: Reuters)

A girl rides her bicycle past a bed of tulips at a public square in Vienna April 22, 2014 (Photo: Reuters)

South Korean rescue workers operate at the site where the capsized passenger ship Sewol sank during the search and rescue operation in the sea off Jindo, at sunset April 22, 2014 (Photo: Reuters)

Lighting flares are released over the sea off Jindo where the capsized passenger ship Sewol sank, as fishing boats emit light during the night rescue operation in Jindo April 22, 2014 (Photo: Reuters)

Tulips bloom in front of the Capitol in Washington, Tuesday, April 22, 2014. The annual burst of color around the Nation's Capital is a sure sign that spring has finally arrived (Photo: AP)

Army soldiers shout slogans as they protest in La Paz, Bolivia, Tuesday, April 22, 2014 (Photo: AP)

This handout photo provided the Smithsonian's National Zoo (Photo: AP)

This June 2013 photo provided by the University of North Florida Office of Research, shows an aerial photo taken from a drone of the Blue J area in northwestern New Mexico. Researchers outfitted a customized drone with a heat-sensing camera to unearth what they believe are ceremonial pits and other features at the site of an ancient village in New Mexico (Photo: AP)

This undated photo provided by the University of North Florida Office of Research shows a surface shot taken by a drone of some of the remnants of stone at the Blue J village in northwestern New Mexico. Researchers outfitted a customized drone with a heat-sensing camera to unearth what they believe are ceremonial pits and other features at the site of an ancient village in New Mexico (Photo: AP)

A pedestrian with an umbrella walks along a street during a heavy snowfall in Russia's Siberian city of Krasnoyarsk, April 22, 2014 (Photo: Reuters)

Indians offer prayers on the banks of the River Yamuna, covered in industrial effluence, on Earth Day in New Delhi, India, Tuesday, April 22, 2014 (Photo: AP)

A supporter holds masks of the country’s main opposition Bharatiya Janata Party (BJP)'s prime ministerial candidate Narendra Modi during an election rally in Hyderabad, India, Tuesday, April 22, 2014 (Photo: AP0

An Italian soldier (C) of the Italian Army's 80th Infantry Regiment of Cassino, gives instructions to Libyan soldiers during a training exercise in Persano, near Salerno, in southern Italy April 15, 2014 (Photo: Reuters)