People walk during a polluted day in Shenyang, Liaoning province, March 31, 2016. (Photo by Reuters/Stringer)

Young monks play inside the Punakha Dzong, Bhutan, April 17, 2016. (Photo by Cathal McNaughton/Reuters)

Young girls carry containers filled with drinking water beside the railway station in Agartala, India, April 20, 2016. (Photo by Jayanta Dey/Reuters)

People cross the street in central Pyongyang, North Korea May 4, 2016. (Photo by Damir Sagolj/Reuters)

An undated handout image provided by UNICEF Germany on 20 December 2016 shows the “UNICEF Photo of the Year 2016” by Iranian freelance photographer Arez Ghaderi. Ghaderi won the first prize for his picture of a girl in a makeshift tent city in the Razavi Khorasan province, Iran, it was announced at a ceremony in Berlin, Germany on 20 December 2016. (Photo by Ariz Ghaderi/EPA/UNICEF Deutschland)

Convention goers dressed as bright colored Wookiees, a fictional species from the US epic space opera franchise Star Wars, prepare for a group photo outside the Comic Con 2016 in San Diego, California, USA, 22 July 2016. The San Diego Comic Con 2016 runs from 21 until 24 July. (Photo by David Maung/EPA)

A barn painted with the U.S. flag is seen in the snow covered field in Kanawha, Iowa, United States, January 16, 2016. Iowa will be the first state to hold its primary, with both Democratic and Republican events being held February 1, 2016. (Photo by Jim Young/Reuters)

Revellers take part in New Year celebrations in Coin, near Malaga, southern Spain, January 1, 2016. (Photo by Jon Nazca/Reuters)