Travellers wait in queue to test for COVID-19 at a train station in Mumbai, India, Tuesday, November 30, 2021. (Photo by Rafiq Maqbool/AP Photo)

Ranger trainees and trainee dogs simulate an ambush against rhino poachers at the Paramount Group Anti-Poaching training and K9 (canine) academy on November 26, 2014 in Magaliesberg, South Africa. One of the largest of its kind in Africa, the Academy will address the ever increasing need for training of Conservation Officers in anti poaching activities, wildlife contraband detection, specialist K9 solutions and Ranger K9 handler training – all of which have proven success rates in combatting and apprehending poachers and their activities. (Photo by Gianluigi Guercia/AFP Photo)

Mongolia's Olympic wrestler Battsetseg Soronzonbold (front) fights with her training partner during a daily training session at the Mongolia Women’s National Wrestling Team training centre in Bayanzurkh district of Ulaanbaatar, Mongolia, July 1, 2016. Battsetseg Soronzonbold became a national hero in her native Mongolia after winning wrestling bronze at the London Olympics and is determined to turn the medal into gold in Rio next month. (Photo by Jason Lee/Reuters)

A commuter exits a closed off station after a subway train derailment, Tuesday, June 27, 2017, in the Harlem neighborhood of New York. A subway train derailed near a station in Harlem on Tuesday, frightening passengers and resulting in a power outage as people were evacuated from trains along the subway line. The Fire Department of New York said a handful of people were treated for minor injuries at around 10 a.m. It said there was smoke but no fire. Delays were reported throughout the subway system. (Photo by Mary Altaffer/AP Photo)

A child attends a training session in a swimming pool on July 10, 2007 in Wuhan of Hubei Province, China. (Photo by China Photos/Getty Images)

A migrant boy sits on railway tracks at a train station in Tovarnik, Croatia, September 20, 2015. (Photo by Antonio Bronic/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)

Passengers travel in an overcrowded train in the eastern Indian city of Patna, February 23, 2010. (Photo by Krishna Murari Kishan/Reuters)