Students attend a stewardess skill training for the upcoming 2017 entrance examination for art majors in colleges in Luoyang, central China's Henan Province, January 4, 2017. Along with how to stand, how to sit is also covered in these classes. (Photo by Li Bo/Xinhua/Barcroft Images)

A protester raises her fist at the entrance of Highway 280 and S. 4th St. as people protest the killing of George Floyd in Minneapolis in downtown San Jose, Calif., on Friday, May 29, 2020. (Photo by Nhat V. Meyer/Bay Area News Group)

A person dressed as the mascot of Tokyo Tower wears a face shield while waiting to greet patrons at the entrance of the 332.9m (1,092ft.) high tower on May 28, 2020, as the city's landmark reopened following the lifting on May 25 of the state of emergency, imposed due to the COVID-19 novel coronavirus outbreak. (Photo by Philip Fong/AFP Photo)

A mannequin wearing a face mask stands at the entrance of a women's clothing store in La Paz, Bolivia, Monday, June 1, 2020. After more than two months of quarantine to curb the spread of the new coronavirus the government authorized the restart of public transport and several industrial and commercial activities. (Photo by Juan Karita/AP Photo)

Riot police stood by the gates of parliament in Nairobi, Kenya, Tuesday, May 14, 2013, during a demonstration against members of parliament who demanded higher wages. Demonstrators released two dozen piglets and poured blood on the pavement to protest the demands for a wage hike. (Photo by Carl de Souza/AFP Photo)

Korean Air flight attendants photograph a therapy dog dressed in a Superman Halloween costume, as part of a program to de-stress passengers at the international boarding gate area of LAX airport in Los Angeles, California, United States, October 27, 2015. (Photo by Lucy Nicholson/Reuters)

A women wearing a mask to protect from extreme smog visits the Tiananmen Gate in Beijing December 8, 2015 as China's capital issues its first ever "red alert" for pollution. (Photo by Damir Sagolj/Reuters)

Swiss police officers stand beside of mock gates of the NEAT Gotthard Base Tunnel inside the event hall for the upcoming opening ceremony near the town of Erstfeld, Switzerland May 31, 2016. The celebrations of the opening of the Gotthard Base Tunnel will start on June 1, 2016. With a length of 57 km (35 miles) crossing the Alps, the Gotthard Base tunnel is the world's longest train tunnel. (Photo by Arnd Wiegmann/Reuters)