Young girls practice acrobatic skills in the Sichuan Provincial Art School July 14, 2008 in Chengdu of Sichuan Province, China. (Photo by China Photos/Getty Images)

A staff member at the Rising Sun Anger Release Bar suits up in protective gear August 8, 2006 in Nanjing of Jiangsu Province, China. (Photo by China Photos/Getty Images)

Ukrainian Air Force officers attend a graduation ceremony at the National University of Defence of Ukraine in Kiev, April 24, 2015. (Photo by Gleb Garanich/Reuters)

A competitor participates in the Tough Mudder challenge near Henley-on-Thames in southern England May 2, 2015. (Photo by Eddie Keogh/Reuters)

A helicopter drops water over a wildfire as a firefighter works to contain it in Benahavis, southern Spain, May 19, 2015. (Photo by Jon Nazca/Reuters)

A woman looks out from her stall selling traditional garments and textiles at a market in Ashgabat February 8, 2012. (Photo by Aman Mehinli/Reuters)

Attendees at Wizard World Comic Con walk through hallways in Chicago, Illinois, United States, August 22, 2015. (Photo by Jim Young/Reuters)

A flock of starlings flies over Lake Leman on an autumn morning in the Lavaux near Grandvaux, Switzerland October 20, 2016. (Photo by Denis Balibouse/Reuters)