Armed Yemeni children sit in the back of a pick up truck with fighters loyal to Yemen's Saudi-backed President Abedrabbo Mansour Hadi in the Dar saad neighbourhood of the southern Yemeni city of Aden on May 10, 2015, as they continue to battle Shiite Huthi rebels. (Photo by Saleh Al-Obeidi/AFP Photo)

Palestinian schoolboys sit in the trunk of a car as they go to school on a rainy day in Khan Younis, in the southern Gaza Strip, October 7, 2015. (Photo by Ibraheem Abu Mustafa/Reuters)

Palestinian children warm themselves by a fire on a stormy day at Shati (beach) refugee camp in Gaza City January 18, 2016. (Photo by Mohammed Salem/Reuters)

A pro-democracy protester wearing a Guy Fawkes mask holds a yellow umbrella and a banner in the part of Hong Kong's financial central district protesters are occupying November 2, 2014. The former British colony of Hong Kong, which returned to Chinese rule in 1997, has witnessed a month of protests calling on the Beijing-backed government to keep its promise of introducing universal suffrage. The protests have for the most part been peaceful, with occasional clashes between the student-led protesters and Beijing supporters seeking to move them from the streets. (Photo by Damir Sagolj/Reuters)

A woman crosses an open sewer as she makes her way to her house in a Christian slum in Islamabad December 4, 2014. (Photo by Zohra Bensemra/Reuters)

A rebel fighter carries his weapon as he moves through a hole in a wall in the old city of Aleppo near the frontline against forces loyal to Syria's President Bashar al-Assad December 28, 2014. (Photo by Jalal Al-Mamo/Reuters)

An internally displaced Afghan girl plays near their shelter at a refugee camp in Kabul January 13, 2015. (Photo by Omar Sobhani/Reuters)

A migrant carries his belongings as he arrives at the Beijing railway station to catch a train in Beijing, Friday, February 13, 2015. (Photo by Andy Wong/AP Photo)