Tiffany Porter of Britain falls after competing in the women's 100 metres hurdles final during the 15th IAAF World Championships at the National Stadium in Beijing, China August 28, 2015. (Photo by David Gray/Reuters)

Second placed Zhang Guowei of China gestures as he celebrates after winning silver in the men's high jump final during the 15th IAAF World Championships at the National Stadium in Beijing, China, August 30, 2015. (Photo by Dylan Martinez/Reuters)

Valentin Arias Delgado and Diana Franco Durango, from Colombia, perform their routine at the Stage style Tango World Championship, in Buenos Aires, Argentina, August 31, 2016. (Photo by Enrique Marcarian/Reuters)

Leopard seal chasing a Gentoo penguin in Antarctica. This image wins the gold prize in the behaviour – mammals category, and the grand prize of World Nature Photographer of the Year. (Photo by Amos Nachoum/World Nature Photography Awards)

The Wadi al-Salam cemetery, Arabic for “Peace Valley”, is seen in Najaf, south of Baghdad, Iraq August 3, 2016. The world's largest cemetery, in Iraq's Shi'ite holy city of Najaf, is expanding at double its usual rate as Shi'ite militias bury their dead from the war against Islamic State. The Wadi al-Salam cemetery, Arabic for “Peace Valley” has a special place in the hearts of Shi'ite Muslims as it surrounds the Mausoleum of their first imam, Ali Bin Abi Talib, a cousin and son-in-law of Prophet Mohammad. (Photo by Alaa Al-Marjani/Reuters)

A soldier helps another with her ear protection at the Terningmoen Camp in Elverum, Norway on March 23, 2017. Soldiers demonstrate their skills and tactics during a contract drill as they train to become part of the world's first all-female special forces unit, the Jegertroppen or “hunter troops”. (Photo by Carolina Reid/NBC News)

Sport category, winner: Yuan Peng. Liu Bingqing and Liu Yujie are twin sisters who have studied and trained in gymnastics since their early childhood in Jining, China. (Photo by Yuan Peng/Sony World Photography Awards)

Sumo wrestler Kaiho eats a “chanko” meal in Nagoya, Japan on July 18, 2017. After ending practice at 10:30 a.m., the wrestlers mingle with fans, sign autographs and pose for photos before the first of their two daily meals. (Photo by Issei Kato/Reuters)