Rebel fighters from the Ahrar al-Sham Islamic Movement fire a heavy machine gun during what they said was an offensive to take the northwestern city of Idlib March 24, 2015. (Photo by Khalil Ashawi/Reuters)

A woman takes her souvenir picture with a white fox in front of ice sculptures illuminated by coloured lights during the opening day of the 31st Harbin International Ice and Snow Festival in the northern city of Harbin, Heilongjiang province, January 5, 2015. The annual Ice and Snow Festival, organized by China National Tourism Administration and local governments, kicked off on Monday in Harbin, one of the coldest cities in China. (Photo by Kim Kyung-Hoon/Reuters)

A food market shows off rows upon rows of dead animals, some of which have been beaten to death. Dogs and chickens can be seen lined up with their mouths hanging wide open. Shoppers even pick up some of the dogs and bats as they look for the best on the market. Retired biologist and amateur photographer Alf Jacob Nilsen took the shocking pictures of the market during a visit to Tomohon Village in Northern Sulawei, Indonesia. Pictured: Flying foxes (bats) for sale at the market. (Photo by Alf Jacob Nilsen/Solent News)

Lucie Clayton instructs pupils in the art of correct posture by balancing a glass and book on their heads at her finishing school in Old Cavendish Street, London. (Photo by William Vanderson/Fox Photos/Getty Images). 25th November 1936

A rescue worker holds an injured boy after what activists said were airstrikes carried out by the Russian air force in Idlib city, Syria December 20, 2015. (Photo by Ammar Abdullah/Reuters)

These greenfinches go head to head in what appears to be a heroic fight or a playfull moment together, inspiration for a new version of “Angry Birds”, in Trezzo Sull'Adda, Italy in March 2013. (Photo by Marco Redaelli/IMP/AbacaPress.com)

“Catch of the Decade”. Can you guess what happened next? Photo location: Katmai National Park, Alaska, USA. (Photo and caption by Aaron Baggenstos/National Geographic Photo Contest)