Children are engulfed by foam during the Bubble Show event in Beijing, China, Sunday, June 26, 2016. Thousands of residents enjoy colored foam churned out by machines along a running track at the event designed for children and parents' interaction. (Photo by Ng Han Guan/AP Photo)

China's Wang Yan performs on the balance beam during the artistic gymnastics women's individual all-around final at the 2016 Summer Olympics in Rio de Janeiro, Brazil, Thursday, August 11, 2016. (Photo by Julio Cortez/AP Photo)

Brazil's Victoria Chamorro failed to stop the ball during their women's classification 7th-8th place water polo match against China at the 2016 Summer Olympics in Rio de Janeiro, Brazil, Friday, August 19, 2016. (Photo by Sergei Grits/AP Photo)

An art wall painting representing performance artist Marina Abramovic by Italian artist Maurizio Cattellan to publicize his upcoming exhibition The Artist is Present, in Shanghai, China, is displayed on a facade of a building, in Milan, Italy, Wednesday, September 19, 2018. (Photo by Luca Bruno/AP Photo)

A family take a souvenir picture next to giant male panda Xiao Liwu, who was born at the San Diego Zoo and will be repatriated to China with his mother Bai Yun, bringing an end to a 23-year-long panda research program in San Diego, California, U.S., April 18, 2019. (Photo by Mike Blake/Reuters)

Wang Zhengqing, a 74 year old pneumoconiosis patient, smokes his pipe at Yangjia Hospital in Wuyi County, Zhejiang Province, China October 19, 2015. Former miner Wang was diagnosed with the disease, which is caused by dust inhalation, when he was 24 and has lived at Yangjia Hospital for ten years. (Photo by Damir Sagolj/Reuters)

In this photo taken on Sunday, July 5, 2015, police officers walk along a giant poster to give an improved appearance, in downtown Ufa, Russia. Ufa will host SOC (Shanghai Cooperation Organization) and BRICS (Brazil, Russia, India, China and South Africa) summits July 7 to July 9, 2015. (Photo by Vadim Braydov/AP Photo)

An explosion at a petrochemical plant is seen in Rizhao, Shandong province, July 16, 2015. According to Xinhua News Agency, a fire broke out after the explosion, which was caused by a liquified hydrocarbon leak at the plant, on Thursday morning. There was no report of casualties yet. (Photo by Reuters/China Daily)