Children wearing uniforms hold toy guns during a military parade game on China's National Day, at Beyou World, a centre children where can experience different kinds of professions, in Beijing, October 1, 2015. (Photo by Reuters/Stringer)

The Cotopaxi volcano, one of the world's highest active volcanoes, spews smoke as seen from El Pedregal, Ecuador, October 22, 2015. Ecuadorian authorities are monitoring activity at Cotopaxi volcano, which prompted Ecuador's President Rafael Correa to maintain a yellow alert for eruptions as bursts of ash keep spewing from the snow-encircled crater of the volcano and falling in gusts on residential communities. (Photo by Guillermo Granja/Reuters)

An activist takes a selfie during a protest ahead of the 2015 Paris Climate Conference, in Paris, Sunday, November 29, 2015. More than 140 world leaders are gathering around Paris for high-stakes climate talks that start Monday, and activists are holding marches and protests around the world to urge them to reach a strong agreement to slow global warming. (Photo by Christophe Ena/AP Photo)

U.S. players push head coach Adam Krikorian into the pool after they defeated the Netherlands in their women's water polo gold medal match during the Aquatics World Championships in Kazan, Russia, August 7, 2015. (Photo by Michael Dalder/Reuters)

Young Buddhist novice monks play at a Tibetan nomadic summer grazing area on July 24, 2015 on the Tibetan Plateau in Yushu County, Qinghai, China. Tibetan nomads face many challenges to their traditional way of life including political pressures, forced resettlement by China's government, climate change and rapid modernization. The Tibetan Plateau, often called “The Roof of the World”, is the world's highest and largest plateau. (Photo by Kevin Frayer/Getty Images)

German Oliver Struempfl competes to set a new world record in carrying one liter beer mugs over a distance of 40 m (131 ft 3 in) in Abensberg September 7, 2014. Struempfl carried 27 mugs over 40 meters to set a new record for the Guinness book of records. (Photo by Michael Dalder/Reuters)

A cat is examined by the jury during the first day of the Super Cat Show 2014, on November 8, 2014 in Rome, Italy. The Super Cat Show 2014, which takes place on the 8th and 9th of November, involves the participation of 800 cats of different breeds from all over the world. (Photo by Giorgio Cosulich/Getty Images)

Alex Plunkett, left, and Sean Hart, both of Arlington, Va., join hundreds participating in the annual International Pillow Fight Day on April 5. Massive pillow fights broke out on the Mall in Washington and in cities around the world. (Photo by Marvin Joseph/The Washington Post)