A dog welcomes a volunteer at the “Ping An A Fu” (“Safe and Happy”) Homeless Animals Rescue Center on September 11, 2006 in Nanjing of Jiangsu Province, China. (Photo by China Photos/Getty Images)

Children of the Roma community play as they cool off in a fountain in the main square of Pristina, Kosovo on June 14, 2017. (Photo by Armend Nimani/AFP Photo)

In this July 15, 2015 photo, Nepalese amputee victims Khendo Tamang, left, and Nirmala Pariyar, both 8, share a single pair of shoes at the Bir Trauma Center in Kathmandu, Nepal. After suffering serious leg wounds in Nepal's massive 2015 earthquake that killed and injured thousands, both girls were brought to the Bir Trauma Center in Kathmandu, to receive single leg amputations. Following their surgeries, Nirmala's relentless cheerfulness drew a still very depressed Khendo close and both found an inseparable friendship which has helped their emotional wounds heal. (Photo by Niranjan Shrestha/AP Photo)

A local resident rests on a bench as Mount Bromo volcano erupts in the background in Ngadisari, Probolinggo, East Java, Indonesia January 5, 2016. (Photo by Darren Whiteside/Reuters)

A woman dressed up for Halloween travels on a Metro train in São Paulo, Brazil on October 30, 2017. (Photo by Cris Faga/Rex Features/Shutterstock)

People walk past debris on May 3, 2015 in Bhaktapur, Nepal. A major 7.8 earthquake hit Kathmandu mid-day on Saturday, and was followed by multiple aftershocks that triggered avalanches on Mt. Everest that buried mountain climbers in their base camps. (Photo by David Ramos/Getty Images)

Framed by the setting sun, an American Bison grazes at the Tallgrass Prairie National Preserve on Tuesday, April 28, 2015, near Strong City, Kan. The buffalo herd at Tallgrass is one of the few herds of wild bison left in the United States. (Photo by Travis Heying/The Wichita Eagle via AP Photo)

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)