A boy and a woman run across a railway track as a train approaches in Chengdu, Sichuan province, China, October 8, 2015. Many residents disregard sign prohibiting this kind of illegal crossing and choose to do so to save time, local media reported. (Photo by Hao Fei/Reuters/Western China Metropolis Daily)

Nuns react at the arrival of Pope Francis at the St. Mary's school to attend a meeting of clergy and religious in Nairobi, Kenya, 26 November 2015. Pope Francis is on a six days visit that will take him to Kenya, Uganda and the Repulic of Central Africa from 25 to 30 November. (Photo by Daniel Dal Zennaro/EPA)

A Bengal tiger licks a glass enclosure during a presentation of Bengial tiger cubs at the Malabon Zoo in Malabon City, north of Manila, Philippines, 14 July 2016. The Bengal tiger cubs, which were born at the zoo, are two months old and named “Tiger Duterte” and “Tiger Leni”. The Malabon Zoo has one of the largest private collections of exotic and endemic animals in the Philippines. (Photo by Mark R. Cristino/EPA)

Saintsetseg Jambaldorj, a member of the Tsaatan ethnic minority, one of the last remaining groups of nomadic reindeer herders in East Taiga, Mongolia, wearing a traditional deel, on July 5, 2016. (Photo by Madoka Ikegami/Barcroft Images)

Students celebrate their A-level results at King Edward VI High School for Girls in Birmingham, England on August 18, 2016. The proportion of top grades achieved by A-level students across the UK has fallen for a fifth year in a row, and girls have caught up with boys in attaining A* grades. (Photo by Joe Giddens/PA Wire)

A devotee smiles as she offers prayers during the Swasthani Brata Katha festival in Kathmandu, Nepal January 12, 2017. (Photo by Navesh Chitrakar/Reuters)

Green algae sits on a beach in Kuwait City, Kuwait, 28 February 2017. The formation of green algae is a normal phenomenon that occurs every year at the shores of Kuwait. (Photo by Raed Qutena/EPA)

A woman already appears to be regretting her choice of heels for the day out during the Grand National Festival at Aintree Racecourse on April 8, 2017 in Liverpool, England. (Photo by Alamy Stock Photos)