Students training to be flight attendants hold books on their heads, chopsticks in their mouths, and papers in between their knees, as they take part in a standing posture practice at a vocational school in Shijiazhuang, Hebei province, China May 4, 2017. (Photo by Reuters/Stringer)

Animals destined for the stage of Radio City Music Hall in New York on November 13, 1986 are led to the stage door by their co-stars, the Rockettes dancers. A variety of animals, including camels, sheep and donkeys, will star in an annual Christmas production. (Photo by G. Paul Burnett/AP Photo)

A Sri Lankan elephant, accompanied by his mahout, browse through a roadside fruit stall in Colombo on January 19, 2015. The Sri Lankan elephant is listed as endangered by the International Union for Conservation of Nature (IUCN) as the population has declined by at least 50 percent over the last three generations, with the species threatened by habitat loss, degradation and fragmentation. (Photo by Lakruwan Wanniarachchi/AFP Photo)

Protesters wear masks, the left in the colors of the Kenyan national flag, as they join others carrying mock coffins and red-painted crosses, symbolizing the blood of the 28 non-Muslims singled out and killed in the recent attack on a bus in Mandera by Somali militant group al-Shabab, outside government offices in downtown Nairobi, Kenya Tuesday, November 25, 2014. (Photo by Ben Curtis/AP Photo)

Ja Kang Song, 71, and Ja Hyun Su, 72, dive for shellfish and are the main breadwinners for their families. In South Korea, 45% of the diving women of Jeju are over the age of 70. Routinely diving to depths of 20m and staying under for an average of two to three minutes, the pressure on the body takes its toll and, like many others, burst eardrums have left Ja Hyun Su deaf. Each season, between seven and 10 women die diving the waters around Jeju Island. (Photo by Andy W. Langton/Age International)

A model backstage ahead of the Lantern Sense show at Fashion Scout during London Fashion Week Autumn/Winter 2016/17 at Freemasons' Hall on February 22, 2016 in London, England. (Photo by Tristan Fewings/Getty Images)

Friends of Li Guojun drive a homemade tank-shaped vehicle in Kangping county, China. Li, a farmer who is a fan of tanks, spent six months with help from his friends to construct the almost 20-foot vehicle which weighs 2.5 tons. (Photo by Sheng Li/Reuters)

Jennifer Lopez, left, is embraced by Pitbull at the end of her performance at the 42nd annual American Music Awards at Nokia Theatre L.A. Live on Sunday, November 23, 2014, in Los Angeles. (Photo by Matt Sayles/Invision/AP Photo)