A visitor views an artwork in an exhibition featuring digital art during China International Big Data Industry Expo 2019 in Guiyang, capital of southwest China's Guizhou Province, May 27, 2019. (Photo: VCG)

Li Junhui(R)/Liu Yuchen of China compete during men's doubles match against Hiroyuki Endo/Yuta Watanabe at the final between China and Japan of Sudirman Cup 2019 in Nanning, capital of south China's Guangxi Zhuang Autonomous Region, May 26, 2019. (Photo: Xinhua)

An engineer stands under a base station antenna of 5G in Huawei's testing system at its Songshan Lake Manufacturing Center in Dongguan, Guangdong province, China May 30, 2019.(Photo: VCG)

A staff member of Ministry of Energy, Science, Technology, Environment and Climate Change displays plastic wastes at Port Klang, Malaysia, May 28, 2019. Developed countries must review their management of plastic waste and stop sending such material to developing countries, Minister of Energy, Science, Technology, Environment and Climate Change Yeo Bee Yin said on Tuesday. (Photo: Xinhua)

A diver of a special South Korean rescue team enters the water at the site of a ship accident, which killed several people, near Margaret Bridge on the Danube river in Budapest, Hungary, May 31, 2019. (Photo: VCG)

Photo taken on June 1, 2019 shows a Virginia State Police cruiser near Municipal Center in Virginia Beach, Virginia, the United States. The death toll rose to 12 plus the suspect shooter in a mass shooting on Friday at the Virginia Beach Municipal Center. (Photo: Xinhua)

Liverpool's English midfielder Jordan Henderson (C) raises the trophy after winning the UEFA Champions League final football match between Liverpool and Tottenham Hotspur at the Wanda Metropolitano Stadium in Madrid on June 1, 2019. (Photo: VCG)

Photo taken on May 24, 2019 shows a group of refugees from Afghanistan at the port of Vathy on Samos, an island in the eastern Aegean, Greece. (Photo: Xinhua)

A villager checks a black chicken at a breeding base in Dahuangyuan Village, Lueyang County, northwest China's Shaanxi Province, May 29, 2019. (Photo: Xinhua)

Graduates celebrate and throw up their caps as the Air Force Thunderbirds fly overhead during the 2019 graduation ceremony at the United States Air Force Academy May 30, 2019, in Colorado Springs, Colorado. (Photo: VCG)