Iraqi troops fire artillery towards Islamic State (IS) group jihadists' positions in west Mosul on March 11, 2017 during the ongoing battle to retake the city from the group. (Photo by Aris Messinis/AFP Photo)

A girl lights a candle as she marks the anniversary of 2015 Nepal earthquake, at Boudhanath stupa in Kathmandu, Nepal April 25, 2017. (Photo by Navesh Chitrakar/Reuters)

A man takes a picture of sea spray as storms hit Cape Town, South Africa, June 7, 2017. (Photo by Mike Hutchings/Reuters)

In this Monday, September 22, 2014 photo provided by the Utah Division of Wildlife Resources, a young cougar is released back into Utah's mountains by the Utah Division of Wildlife Resources in an undisclosed site in central Utah. State wildlife officials received reports of the cougar roaming Sunday afternoon in a residential area of the city's eastern flank, a few miles from the base of the Wasatch Mountains. Authorities say cougars generally avoid humans but sometimes enter neighborhoods close to their mountain habitats. (Photo by Steve Gray/AP Photo/Utah Division of Wildlife Resources)

West Berliners crowd in front of the Berlin Wall as they watch East German border guards demolish a section of the wall on November 11, 1989. (Photo by Gerard Malie/AFP Photo)

Russia's Maria Stavitskaia performs during the ladies short program at the Rostelecom Cup ISU Grand Prix of Figure Skating in Moscow November 14, 2014. (Photo by Grigory Dukor/Reuters)

Shoppers wrestle over a television as they compete to purchase retail items on “Black Friday” at an Asda superstore in Wembley, north London November 28, 2014. Britain's high streets, malls and online sites were awash with discounts on Friday as more retailers than ever embraced U.S.-style “Black Friday” promotions, seeking to kickstart trading in the key Christmas period. In the United States the Friday following the Thanksgiving Day holiday is called Black Friday because spending usually surges and indicates the point at which American retailers begin to turn a profit for the year, or go “into the black”. (Photo by Luke MacGregor/Reuters)