A Polisario fighter sits on a rock at a forward base on the outskirts of Tifariti, Western Sahara, September 9, 2016. At a rocky outpost in Western Sahara, a new generation of soldiers who have never known war are mobilising as tensions resurface in one of Africa's oldest disputes after a quarter century of uneasy peace. (Photo by Zohra Bensemra/Reuters)

In this Tuesday, August 2, 2016 photo released by Xinhua News Agency, people stand on a platform as the Transit Elevated Bus TEB-1 conducting a test run after it unveiled in Qinhuangdao, north China's Hebei Province. The 72-feet long and 25-feet wide Transit Elevated Bus (TEB) powered by electricity can carry more than hundreds passengers, is designed to go over the normal traffic to help ease traffic congestion without having to dig new tunnels or build elevated rail tracks. (Photo by Luo Xiaoguang/Xinhua via AP Photo)

Gymnast Ahmad al-Sawas performs gymnastic moves near damaged buildings in the rebel-held Bustan al-Qasr neighbourhood of Aleppo, Syria March 26, 2016. As Syrian gymnast Ahmad al-Sawas watched his country fall apart, his Olympic dream collapsed too. The last national champion before the fighting began, he knew that supporting the anti-government side in the five-year-old civil war would prevent him from being selected for the Rio Games. (Photo by Abdalrhman Ismail/Reuters)

Igor Gavrilov, the main taxidermist of the Zoological centre at Tel Aviv University, works on a taxidermied animal, part of a collection which will be housed at the Steinhardt Museum of Natural History, a new Israeli natural history museum set to open next year in Tel Aviv, Israel June 8, 2016. Legions of insects, sea creatures and ancient fossils are lining up in a new museum shaped liked a giant Noah's Ark, telling the story of a crucial evolutionary byway across Israel. (Photo by Nir Elias/Reuters)

An Afghan boy looks through the scope of a toy gun, as other children ride on swings during the first day of the Muslim holiday of Eid al-Fitr, which marks the end of the holy month of Ramadan, in Kabul, Afghanistan June 25, 2017. (Photo by Omar Sobhani/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)

An anti-government protester wearing a Guy Fawkes mask stands with a shield near flames from molotov cocktails thrown at a water cannon by anti-government protesters during riots in Caracas in this April 20, 2014 file photo. (Photo by Jorge Silva/Reuters)

Three young women in their 20s brawling on a busy street on the route from the track to the town centre during day four of the William Hill St Leger Festival at Doncaster Racecourse, England on September 14, 2019. (Photo by Nb press ltd)