A train attendant helps a passenger to adjust her seat at the business class carriage on a CRH 380A bullet train Thursday, June 16, 2011. (Photo by Reuters/China Daily)

A woman touches a robot at the 2018 World Robot Conference in Beijing on August 15, 2018. The conference will be held from 15 to 19 August and will include a conference on robotics, an exhibition and a robot competition with the participation of robotics enterprises to showcase their robot products. (Photo by Wang Zhao/AFP Photo)

A 2.4 kg chicken is pictured next to 14,600,000 bolivars, its price and the equivalent of 2.22 USD, at a mini-market in Caracas, Venezuela on August 16, 2018. It was the going price at an informal market in the low-income neighborhood of Catia. (Photo by Carlos Garcia Rawlins/Reuters)

An American soldier walks ahead of an MKIV (Mark IV) British-made tank, circa 1918. (Photo by Hulton Archive/Getty Images)

Sunset on Brighton beach on February 24, 2019 in Brighton, England. (Photo by Andrew Hasson/Getty Images)

Anti-frost candles burn in apricot plantations to protect flowering buds and blossoms from frost in the midst of the Swiss Alps, in Saxon, Canton of Valais, Switzerland, 05 April 2019. With an unusually low temperature forecast for the season, fruit growers try to protect their buds from frost damage with two different means, icy water or large candles. (Photo by Valentin Flauraud/EPA/EFE)

A guest proposes to his companion as they arrive for the screening of “Mektoub, My Love: Intermezzo” during the 72nd annual Cannes Film Festival, in Cannes, France, 23 May 2019. The movie is presented in the Official Competition of the festival which runs from 14 to 25 May. (Photo by Julien Warnand/EPA/EFE)

Greece's Stefanos Tsitsipas falls after diving to return a shot against Switzerland's Stan Wawrinka during their fourth round match of the French Open tennis tournament at the Roland Garros stadium in Paris, Sunday, June 2, 2019. (Photo by Christophe Ena/AP Photo)