An attendee is seen at the Bristol Renaissance Faire in Bristol, Wisconsin, the United States, July 28, 2019. (Photo by Joel Lerner/Xinhua)

A cosplayer poses for a photo during the Otakon 2019 at the Walter E. Washington Convention Center in Washington D.C., the United States, on July 27, 2019. The three-day Otakon is an annual event for Asian pop culture. (Xinhua/Liu Jie)

European Central Bank (ECB) President Mario Draghi speaks during a press conference held at the ECB headquarters in Frankfurt, Germany, on July 25, 2019. The ECB kept key interest rates for the euro area unchanged but revised forward guidance to open doors for possible monetary policy easing. (Xinhua/Lu Yang)

A woman wears Burang clothes in Burang County of Ali, southwest China's Tibet Autonomous Region, July 22, 2019. Burang clothes, traditional wearing in Burang County of Ali, has a history of more than 1,000 years. One suit may weigh about 25 kilograms because it is decorated with gold, silver, pearls and other jewels. (Xinhua/Chogo)

Xu Jiayu of China reacts before the men's 50m backstroke final at the Gwangju 2019 FINA World Championships in Gwangju, South Korea, July 28, 2019. (Xinhua/Xia Yifang)

Combination photo taken on July 10, 2019 shows Gyawang Norbu (Top L), Dorje Tsring (Top R), Chimei Tashi (Bottom L) and Gyal Bu, mountain guides from Tibet Himalaya Mountaineering Guide School in Lhasa, southwest China's Tibet Autonomous Region. Tibet Himalaya Mountaineering Guide School celebrates its 20th anniversary in Lhasa, capital of southwest China's Tibet Autonomous Region, on July 12, 2019. Founded in 1999, Tibet Himalaya Mountaineering Guide School, the first professional mountaineerin

U.S. President Donald Trump responds to reporters before leaving the White House in Washington D.C. on July 24, 2019. Trump vetoed congressional resolutions that intend to block the Trump administration's efforts to sell weapons to Saudi Arabia and the United Arab Emirates. (Photo by Ting Shen/Xinhua)

Combination photo taken on July 10, 2019 shows Nyawang Tashi (L) and Lhok Chong, mountain guides from Tibet Himalaya Mountaineering Guide School in Lhasa, southwest China's Tibet Autonomous Region. Tibet Himalaya Mountaineering Guide School celebrates its 20th anniversary in Lhasa, capital of southwest China's Tibet Autonomous Region, on July 12, 2019. Founded in 1999, Tibet Himalaya Mountaineering Guide School, the first professional mountaineering training school in China, has trained around 3

Yemeni students play the violin during a music class at the Cultural Center in Sanaa, Yemen, July 24, 2019. (Photo by Mohammed Mohammed/Xinhua)

People participate in the public boxing practice in Moscow, Russia, on July 21, 2019. Over 4,000 people took part in a boxing training session during the 3rd international boxing day on Red Square, trying to break the Guinness World Record for Mass Boxing Training. (Xinhua/Evgeny Sinitsyn)

Sun Yang of China reacts after the men's 800m freestyle final at the Gwangju 2019 FINA World Championships in Gwangju, South Korea, July 24, 2019. (Xinhua/Tao Xiyi)

Former U.S. Special Counsel Robert Mueller swears before the House Judiciary Committee during a hearing about his investigation into alleged Russian interference in the 2016 U.S. presidential election and whether Trump had obstructed justice, on Capitol Hill in Washington D.C., the United States, on July 24, 2019. (Photo by Ting Shen/Xinhua)

A Hindu woman is seen at Pashupatinath Temple in Kathmandu, Nepal, July 22, 2019. (Xinhua/Sulav Shrestha)

Newly elected Conservative party leader Boris Johnson poses outside the Conservative Leadership Headquarters in London, Britain on July 23, 2019. (Photo by Alberto Pezzali/Xinhua)

Combination photo taken on July 10, 2019 shows Tashi Kunbu (Top 1st L), Pubu Tsering (Top 2nd L), Suonam Tsering (Bottom L) and Lhudar, mountain guides from Tibet Himalaya Mountaineering Guide School in Lhasa, southwest China's Tibet Autonomous Region. Tibet Himalaya Mountaineering Guide School celebrates its 20th anniversary in Lhasa, capital of southwest China's Tibet Autonomous Region, on July 12, 2019. Founded in 1999, Tibet Himalaya Mountaineering Guide School, the first professional mounta

Theresa May gives a farewell speech outside 10 Downing Street in London, Britain, July 24, 2019. Newly-elected Conservative Party leader Boris Johnson took office as the British prime minister amid the rising uncertainties of Brexit. The latest development came after Theresa May formally stepped down as the leader of the country and Johnson was invited by the Queen to form the government. (Xinhua/Han Yan)

A man attends a Thangka display ritual at the Tashilhunpo Monastery in Xigaze, southwest China's Tibet Autonomous Region, July 15, 2019. (Xinhua/Chogo)

A child cools off at a fountain in Washington D.C., the United States, on July 20, 2019. (Xinhua/Liu Jie)

Ursula von der Leyen attends a press conference after being elected the next president of the European Commission at the headquarters of European Parliament in Strasbourg, France, July 16, 2019. (Xinhua/Zhang Cheng)

David Marcus, head of Facebook's blockchain subsidiary Calibra, testifies before the Senate Banking, Housing and Urban Affairs Committee on "Examining Facebook's Proposed Digital Currency and Data Privacy Considerations" on Capitol Hill in Washington D.C., the United States, on July 16, 2019. (Xinhua/Liu Jie)

A miner carries buckets of sulfur from the Ijen volcano in Banyuwangi, East Java, Indonesia, July 18, 2019. More than 200 miners work at traditional sulfur mines near Indonesia's Ijen volcano. They are paid seven to eight dollars per day and do not wear special protective clothing while working. (Xinhua/Bukbis Chandra Ismeth)

Svetlana Romashina of Russia competes during the artistic swimming women's solo free final at FINA World Championships in Gwangju, South Korea on July 17, 2019. (Xinhua/Bai Xuefei)

A student wears a plastic bag during a campaign to promote awareness for plastic pollution in Kolkata, India, on July 19, 2019. (Xinhua/Tumpa Monday)