A riot policeman watches as a police vehicle burns in Braamfontein, Johannesburg, South Africa, Tuesday, October 25, 2016. Rioters in South Africa set a police vehicle on fire Tuesday and stoned vehicles near a Johannesburg university that has been the scene of sometimes violent protests by students demanding free education. The violence broke out in streets near the University of the Witwatersrand at around the same time that student protesters met and marched off the campus, South African media reported. (Photo by Yeshiel Panchia/AP Photo)

A quartet of showgirls in costume sit at an outdoor table and drink from mugs at Disneyland amusement park, Anaheim, California, 1955. (Photo by Loomis Dean/The LIFE Picture Collection/Getty Images)

An internally displaced Afghan girl holds a child at a refugee camp in Kabul, Afghanistan May 31, 2016. (Photo by Mohammad Ismail/Reuters)

Clash of the storms, New Mexico, US by Camelia Czuchnicki. “A clash between two storm cells in New Mexico, US, each with its own rotating updraft. The curved striations of the oldest noticeable against the new bubbling convection of the newer. It was a fantastic sight to watch and it’s the rarity of such scenes that keep drawing me back to the US Plains each year”. (Photo by Camelia Czuchnicki/Weather Photographer of the Year 2016)

In this photo taken on Friday, July 14, 2017, a student at a paramilitary camp for children calls the rank to attention outside Kiev, Ukraine. As the deadly conflict in eastern Ukraine entered its third year, some parents in Ukraine are anxious to make sure their children are ready to fight it, instead of swimming and playing volleyball. (Photo by Efrem Lukatsky/AP Photo)

The battle by Jose Garcia, US. Category: bird behaviour. A great white heron (Ardea herodias occidentalis) fighting a green snake in the Florida Everglades. The fight lasted for nearly 20 minutes with the heron having to release its prey. (Photo by Jose Garcia/2017 Bird Photographer of the Year Awards)

A car rolls south along the Dalton Highway near Coldfoot, Alaska, USA, 03 September 2017. Stretching 414 miles (666 kilometers) north from central Alaska to Prudhoe Bay, the Dalton Highway is one of America's northernmost roads and arguably its most remote. (Photo by Jim Lo Scalzo/EPA)

Ethnic “Kam” (also known as Dong) women get ready for a traditional wedding ritual known as the “steal the chicken at the drum tower” in a minority Dong village in southwestern Chinese city of Congjiang, Guizhou province, China January 29, 2017. The ceremony held in the ethnic Kam minority village of Gantuan in Guizhou province is based on a tradition dating back some 500 years that was revived and modified in the 1990s for villagers and tourists. (Photo by Tyrone Siu/Reuters)