Karis, an 8 week old lion cub, growls at a pumpkin as she explores a Halloween treat put in her enclosure by staff at Blair Drummond Safari Park near Stirling, Scotland, Tuesday, October 29, 2013. (Photo by Andrew Milligan/AP Photo/PA Wire)

Men are held by Iraqi national security agents, to be interrogated at a checkpoint, as oil fields burn in Qayara, south of Mosul, Iraq, Saturday, November 5, 2016. Islamic State fighters launch counterattacks in the thin strip of territory Iraqi special forces have recaptured in eastern Mosul, highlighting the challenges ahead as the battle moves into more densely populated neighborhoods where coalition air power must be used more selectively. (Photo by Felipe Dana/AP Photo)

A man exercises in the early morning on a hilltop overlooking Kabul, Afghanistan March 3, 2016. (Photo by Mohammad Ismail/Reuters)

People wash in water from a broken water pipeline on the outskirts of Kolkata, India, March 30, 2016. (Photo by Rupak De Chowdhuri/Reuters)

An abandoned tank left by Boko Haram, February 20, 2016, seen on the road to Michika, Nigeria – a town formerly occupied by the insurgents. On April 14, 2014, 300 schoolgirls in the Chibok village in Nigeria were kidnapped by the terrorist group, Boko Haram. Two years later, the majority of these girls are still missing. According to the Global Terrorism Index Report 2015, Boko Haram, which operates mainly in Nigeria, has become the most deadly terrorist group in the world. (Photo by Danielle Villasana)

Civilians present their rations cards in order to receive humanitarian food aid being distributed by the Iraqi Red Crescent, in the eastern side of Mosul, Iraq, Tuesday, January 31, 2017. Iraqi forces declared Mosul's eastern half fully liberated, just over three months after the operation to retake the city from IS was formally launched in October. (Photo by Khalid Mohammed/AP Photo)

Festival goers splash through a muddy puddle at Worthy Farm in Somerset, on the third day of the Glastonbury music festival June 27, 2014. (Photo by Cathal McNaughton/Reuters)

Afghan women learn how to make a doll at a workshop sponsored by a Malaysian NGO called Mercy that seeks to help local females to empower themselves on April 15, 2010 in Kandahar, Afghanistan. (Photo Majid Saeedi/Getty Images)