Workers sleep on a railway track under repair in New Delhi, India, June 15, 2018. (Photo by Saumya Khandelwal/Reuters)

Flames from the County fire burn above Cache Creek Casino Resort on Saturday, June 30, 2018, in Capay, Calif. (Photo by Noah Berger/AP Photo)

Newlyweds pose on a zebra crossing for wedding photographers during the 2018 soccer World Cup in Samara, Russia, Sunday, July 8, 2018. (Photo by Frank Augstein/AP Photo)

Indian children dressed up as the Hindu deities Rama and Sita take a selfie photograph at an event to celebrate the Diwali festival in Ajmer in western Rajasthan state on November 6, 2018. (Photo by Shaukat Ahmed/AFP Photo)

Russian Foreign Ministry spokeswoman Maria Zakharova dances during the reception in honour of heads of the delegations at the Russia-ASEAN summit in Sochi, Russia, May 19, 2016. (Photo by Host photo agency via Reuters)

A student, wearing a traditional costume and headdress, stands in line for interviews during a recruitment held by an airline company, hoping to stand out from more than 500 candidates for airline stewardess positions, in Chengdu, Sichuan Province, China, May 27, 2016. (Photo by Reuters/Stringer)

In this October 21, 2015, file photo, a young man rides a hoverboard along a Manhattan street toward the Empire State Building in New York. More than 500,000 hoverboards are being recalled after reports that they can burst into flames. The Consumer Product Safety Commission said Wednesday, July 6, 2016, it has received 99 reports of battery packs in the two-wheel motorized scooters catching fire or exploding that causing burns or property damage. The recalled hoverboards were made by eight companies. (Photo by Kathy Willens/AP Photo)

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)