Mohammad, a 13-year-old fighter from the “Free Syrian Army”, plays with a cat in Aleppo's Bustan al-Basha district, Syria October 28, 2013. Mohammad joined the Free Syrian Army after his father died during clashes with the Syrian regime. The gun he is using was his father's. (Photo by Molhem Barakat/Reuters)

A woman wearing a mask reacts at her garden which locates next to chimneys of coal-fired power plant in Shijiazhuang, Hebei province, China, January 28, 2015. Beijing introduced tougher regulations this year to combat pollution, keen to overhaul China's unwanted image of smog-choked cities, fouled waterways and heavy-metal tainted soil. (Photo by Kim Kyung-Hoon/Reuters)

The Villarrica Volcano is seen at night from Pucon town, Chile, July 12, 2015. Villarrica, located near the popular tourist resort of Pucon, is among the most active volcanoes in South America. (Photo by Cristobal Saavedra/Reuters)

Alexo Carmona, 2, looks at Coco, a two-year-old pony, in downtown Havana, in this March 6, 2015 file photo. Nearly a quarter of a million people follow the Reuters Instagram account – and it's still growing fast. To mark the mid-point of 2015, Reuters has compiled the twenty most-liked pictures so far. This picture was 20th most popular. (Photo by Alexandre Meneghini/Reuters)

Competitors prepare backstage before the 2015 Brazil Miss and Mister Fitness contest in Sao Paulo, Brazil, June 18, 2015. Some 96 men and women from all across the country competed in the event. (Photo by Paulo Whitaker/Reuters)

In this June 8, 2015 photo, Omkarnath, who goes by the name “Medicine Baba”, pays his reverence at a neighborhood temple as he begins his day in New Delhi, India. The chatty, 79-year-old retired blood-bank technician has been collecting unused prescription drugs from the affluent for the past eight years, and distributing whatever hasn't expired to patients who need medicines they cannot afford. (Photo by Saurabh Das/AP Photo)

Riot police scuffle with pro-democracy students after hundreds of protesters stormed into a restricted area at the government headquarters, after a rally ahead of the October 1 “Occupy Central” civil disobedience movement in Hong Kong September 27, 2014. Hong Kong riot police used pepper spray on Saturday to disperse dozens of students who had stormed government headquarters, but an equal number held their ground in protests against Beijing's tightening grip on the city. (Photo by Tyrone Siu/Reuters)

Miranda Kerr attends Carine Roitfeld & Stephen Gan celebration of the launch of CR Fashion Book N.5 in Paris, Tuesday, September 30, 2014. (Photo by Zacharie Scheurer/AP Photo)