A Philippine boy collects used plastic bottles to be sold at a junk shop at Divisoria market in Manila on November 29, 2017. (Photo by Noel Celis/AFP Photo)

Dancers of the Czech National Ballet warm up backstage during a performance of “The Nutcracker – A Christmas Carol” at the National Theatre in Prague, Czech Republic, late 16 December 2017. Peter I. Tchaikovsky's “The Nutcracker”, one of his most famous compositions and seasonal ballets, premiered in St. Petersburg, Russia, on 18 December 1872, celebrates its 125th anniversary this year. (Photo by Martin Divisek/EPA/EFE)

Members of Japan's idol group “Virtual Currency Girls” wearing cryptocurrency-themed masks perform in their debut stage in Tokyo, Japan, January 12, 2018. Japanese female idols have teamed up to form the ‘Virtual Currency Girls’ group to promote the knowledge of cryptocurrencies through entertainment. Each of its 8 members represents a cryptocurrency: bitcoin cash, bitcoin, ether, neo, nem, ripple, mona, and cardano. (Photo by Kim Kyung-Hoon/Reuters)

Tube passengers take a selfie next to a London underground roundel designed for the launching of the Night Tubes on display at Oxford Circus underground station in London, Britain, 19 August 2016. The long delayed Night Tubes service launched on 19 August. The 24-hour service will operate on Fridays and Saturdays. (Photo by Hannah Mckay/EPA)

American students going wild during their Spring Break week-long recess in Cancun, Mexico on March 10, 2007. (Photo by Keystone USA/ZUMA Press/Rex Features/Shutterstock)

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)

Laborers lay down upon a field to cut off the tulips that remained uncut by the tractor in Den Helder, Netherlands April 22, 2017. (Photo by Cris Toala Olivares/Reuters)

An aerial view taken with a drone shows the autumnally colored Fuerst-Pueckler-Park near Cottbus, eastern Germany, Saturday, October 29, 2016. The park, composed with great sensitivity in the 19th century by Prince Hermann von Pueckler-Muskau, is considered as one of the last great German landscape gardens. (Photo by Patrick Pleul/DPA via AP Photo)