“DC3 Wreck”. A capture of a US military DC3 plane wreck at the southern black beach in Iceland. Photo location: Iceland. (Photo and caption by Naian Feng/National Geographic Photo Contest)

A man in a Donald Trump mask joins hundreds of other protesters and activists as they march during a demonstration near a midtown hotel which is hosting a black-tie fund-raiser for the state Republican Party on April 14, 2016 in New York City. (Photo by Spencer Platt/Getty Images)

Cloud inversion taken at Sunrise in Mam Tor, Derbyshire, UK on August 30, 2016. (Photo by David Zdanowicz/Rex Features/Shutterstock)

In collaboration with the Pennsylvania Department of Transportation, Allegheny College art students repurpose used street signs as art materials to create the PennDOT Road Sign Sculpture Garden in Meadville, Pennsylvania, USA on August 19, 2017. (Photo by Brian Cahn/ZUMA Wire/Rex Features/Shutterstock)

A man walks his dog as the sun sets in a park in Frankfurt, Germany, Monday, September 18, 2017. Cool damp weather is set to continue in this part of Germany for the next few days with temperatures in the mid teens Celsius. (Photo by Michael Probst/AP Photo)

An army dog stands up as retiring soldiers salute their guard post before retirement in Suqian, Jiangsu province, China on November 29, 2017. (Photo by Reuters/China Stringer Network)

Armed female members of the militant Palestinian group Islamic Jihad carry Kalashnikov assault rifles as they take part in a rally to protest against US President Donald Trump's decision to recognise Jerusalem as the capital of Israel, in Gaza City on December 11, 2017. (Photo by Mohammed Abed/AFP Photo)

North Korean soldiers march during a military parade marking the 105th birth anniversary of the country's founding father Kim Il Sung in Pyongyang, North Korea, April 15, 2017. (Photo by Damir Sagolj/Reuters)