Yaks head towards the Everest base camp in Solukhumbu District April 28, 2014. (Photo by Navesh Chitrakar/Reuters)

A model in Mongolia costumes prepares backstage in Xiangshawan Desert, also called Sounding Sand Desert on July 18, 2013 in Ordos of Inner Mongolia Autonomous Region, China. Xiangshawan is China's famous tourist resort in the desert. It is located along the middle section of Kubuqi Desert on the south tip of Dalate League under Ordos City. Sliding down from the 110-metre-high, 45-degree sand hill, running a course of 200 metres, the sands produce the sound of automobile engines, a natural phenomenon that nobody can explain. (Photo by Feng Li)

Protesters clad in improvised protective gear prepare for a clash with police in central Kiev, Ukraine, Monday, January 20, 2014. After a night of vicious streets battles, anti-government protesters and police clashed anew Monday in the Ukrainian capital Kiev. (Photo by Evgeny Feldman/AP Photo)

A woman walks against blowing snow in Evanston, Illinois, on February 8, 2014. (Photo by Nam Y. Huh/Associated Press)

Actress Zendaya arrives at the 27th Annual Kids' Choice Awards in Los Angeles, California March 29, 2014. (Photo by Danny Moloshok/Reuters)

An Armatix employee holds a “smart gun” by the company at the Armatix headquarters in Munich May 14, 2014. The gun is implanted with an electronic chip that allows it to be fired only if the shooter is wearing a watch that communicates with it through a radio signal. If the gun is moved more than 10 inches (25 cm) from the watch, it will not fire. A Maryland gun shop owner has dropped his plan to be the first in the United States to sell the so-called “smart gun” after a backlash that included death threats. (Photo by Michael Dalder/Reuters)

A costumed fan attends Comic-Con International 2014 – Day 1 on July 24, 2014 in San Diego, Calif. (Photo by Joe Scarnici/FilmMagic/Getty Images)

A participant covered in coloured powder gestures as she stands near a Syrian army soldier during “I Love Damascus” marathon at Umayyad Square in Damascus, Syria October 7, 2016. (Photo by Omar Sanadiki/Reuters)