Rohingya refugee sisters Nur Kaida (R) and Ruhana hug each other at their shelter at the Palongkhali refugee camp near Cox's Bazar, Bangladesh December 21, 2017. (Photo by Marko Djurica/Reuters)

The buildings of the banking district are seen through thousands of rain drops on a glass railing in central Frankfurt, Germany, Wednesday, January 11, 2017. (Photo by Michael Probst/AP Photo)

A worker spreads paddy crop for drying in a rice mill complex on the outskirts of Ahmedabad February 3, 2011. (Photo by Amit Dave/Reuters)

A Virgin Atlantic passenger plane flies in the sky with the moon seen in the background, in London, Britain January 19, 2016. (Photo by Toby Melville/Reuters)

A National Bolivarian Police officer rescues a man who was being attacked by protesters, who then threw rocks at them, during a protest demanding food a few blocks from Miraflores presidential palace in Caracas, Venezuela, Thursday, June 2, 2016. Venezuela is seeing rising frustration with widespread food shortages and triple-digit inflation. (Photo by Fernando Llano/AP Photo)

A tank's barrel is seen on the course of the Tank Biathlon competition during the International Army Games 2016 in Alabino, outside Moscow, Russia, July 30, 2016. (Photo by Maxim Zmeyev/Reuters)

Early morning storms over the Masai Mara National Reserve, Kenya on August 26, 2016. (Photo by Action Press/Rex Features/Shutterstock)

A man poses in front of a portrait of late Chinese Chairman Mao Zedong during the opening of an exhibition of Mao related art in Beijing, China, September 8, 2016. (Photo by Thomas Peter/Reuters)