Students exercise in body training at Bishan Vocational Education Center in Chongqing, southwest China, January 13, 2016. These students were trained to be stewardesses of the high-speed train. (Photo by Xie Jie/Xinhua)

Deers walk past Indonesia's honour guard as they wait for the arrival of Saudi Arabia's King Salman bin Abdul Aziz at the presidential palace in Bogor on March 1, 2017. Cheering crowds welcomed King Salman on March 1 as he began the first visit by a Saudi monarch to Indonesia for almost 50 years, seeking stronger economic ties with the world's most populous Muslim-majority country. (Photo by Adek Berry/AFP Photo)

A hippopotamus is sprayed with water on a hot summer day at Anna National Zoological Park in Chennai, India on April 26, 2017. (Photo by Arun Sankar/AFP Photo)

Party-goers partake in a festival better known as Holi One, during International Workers Day in Johannesburg, South Africa, 01 May 2015. The colour festival promotes togetherness as well as colourness in everday life. May Day is observed worldwide every year on 01 May. (Photo by Kevin Sutherland/EPA)

A gibbon drinks from a soft drink bottle, given by a tourist, at a zoo in Kunming, Yunnan province, June 18, 2015. (Photo by Wong Campion/Reuters)

Balinese man watches Mount Agung volcano almost covered with clouds as he stands at a temple in Karangasem, Bali, Indonesia, Tuesday, September 26, 2017. An increasing frequency of tremors from the volcano indicates magma is continuing to move toward the surface and an eruption is possible, a disaster agency official said Tuesday. Tourists are cutting short their stay to the island, where an eruption would force the airport to close and strand thousands. (Photo by Firdia Lisnawati/AP Photo)

Spectators pass through security screening ahead of the New Year's Eve celebration in Times Square in New York, on Sunday, December 31, 2017. (Photo by Peter Morgan/AP Photo)

In this January 3, 2018 photo several female Gelada baboons, also known as bleeding-heart baboons, cuddle with their youngs in order to keep warm at the Wilhelma zoo in Stuttgart, Germany. (Photo by Sebastian Gollnow/DPA via AP Photo)