A sledding dog is covered in ice after spending the night in the open air with his musher at the polar base of Val-Cenis, as they ready for the next stage of the 12th edition of “La Grande Odyssee” sledding race across the Alps on January 17, 2016 in Val Cenis Lanslevillard. (Photo by Jean-Philippe Ksiazek/AFP Photo)

China's Wang Yan performs on the balance beam during the artistic gymnastics women's individual all-around final at the 2016 Summer Olympics in Rio de Janeiro, Brazil, Thursday, August 11, 2016. (Photo by Julio Cortez/AP Photo)

Life-size sеx dolls are displayed during the 2016 AVN Adult Entertainment Expo at the Hard Rock Hotel & Casino on January 20, 2016 in Las Vegas, United States. (Photo by Gabe Ginsberg/FilmMagic)

Daniel Fox inside the Mendenhall Glacier, in September 2014, in Juneau, Alaska. Driving in an open-roofed jeep is no longer the fashionable way to see wildlife – as this adventurer shows. A keen wildlife photographer has circled islands in the south of Alaska, the United States, in a kayak to see spectacular scenery and animals. Daniel Fox, 40, from San Francisco spent three months travelling around the islands by kayak, meeting sea lions and brown bears along the way. (Photo by Daniel Fox/Barcroft Media)

The Enemy, 1944. With the outbreak of world war two, photojournalism was enlisted in defence of Mother Russia. In this photo by Anatoli Egorov, who was wounded in action, corporal Stepan Vasiljevich Ovcharenko shoots at enemy troops with a machine gun. (Photo by Anatoli Egorov/Lumiere Brothers Center for Photography)

Participants run through the streets of the Back Bay during the 16th annual Santa Speedo Run in Boston, Massachusetts, December 12, 2015. (Photo by Brian Snyder/Reuters)

In this March 14, 2015 photo, tourists take pictures from a viewing area at Iguazu Falls in Brazil. From walkways and bridges, viewers can count 270 water falls almost 100 meters (330 feet) high. (Photo by Jorge Saenz/AP Photo)

An American soldier walks ahead of an MKIV (Mark IV) British-made tank, circa 1918. (Photo by Hulton Archive/Getty Images)