A pile of destroyed cars of teachers sits outside Briarwood elementary school in Oklahoma City, Oklahoma May 22, 2013. Rescue workers with sniffer dogs picked through the ruins on Wednesday to ensure no survivors remained buried after a deadly tornado left thousands homeless and trying to salvage what was left of their belongings. Curvature of horizon in the photo is due to an ultra-wide angle lens. (Photo by Rick Wilking/Reuters)

Gorillas at Royal Burgers’ Zoo, Arnhem, Netherlands, on November 28, 2013. (Photo by Vidi Photo/Startraks Photo New York)

Jack, a Lurcher from Dogs Trust Salisbury, walks past a window display of models in a Dogs Trust shop window in Salisbury, as part of a campaign to discourage the impulse buying of dogs ahead of Valentine's Day, on February 10, 2014. (Photo by Matt Alexander/PA Wire)

A chevrotain or mouse deer feeds in its enclosure at Zurich Zoo, Zurich, Switzerland, October 17, 2012. (Photo by Patrick B. Kraemer/AP)

Retired builder Vasili Sidamonidze, 70, poses for a portrait at his home in Gori, Georgia, December 6, 2016. “Unfortunately, Stalin is not popular nowadays. Our people don't respect him. Only we, members of the (Communist) Party, respect him”, Sidamonidze said. “I always try to attend Stalin's birthday anniversaries in Gori. Unfortunately many people don't want to join us even if they live nearby. They look at us from their windows”. (Photo by David Mdzinarishvili/Reuters)

Young Korean women wearing hanbok (Korean traditional dress) walk inside Gyeongbok Palace on March 27, 2016 in Seoul, South Korea. There has been a trend in recent years for the young Koreans to wear the traditional Korean dress, Hanbok. Wearing the traditional dress, they will walk around downtown Seoul on weekends taking selfies, and share their memories with friends on social media, and also to promote their traditional dress to foreign visitors. (Photo by Jean Chung/Getty Images)

Pupils of the Dao ethnic tribe return home from school along a hillside path at Suoi Thau village in Hoang Su Phi district of Vietnam's northern province of Ha Giang, located at the border with China, September 18, 2015. (Photo by Reuters/Kham)

Giant panda Meng Meng plays on a tree at a Siberian tiger-breeding base in Changchun, China on December 10, 2015. (Photo by Xu Chang/Xinhua Press/Corbis)