A rescuer gauges the density of carbon monoxide in the smog at the coal mine accident site in Chongqing, Southwest China, Dec 4, 2020. At least 23 people were killed and one person was rescued after an accident due to excessive levels of carbon monoxide in a coal mine in Chongqing, rescuers said on Saturday. (Photo: Xinhua)

Technical personnel monitor the rendezvous and docking of the ascender of China's Chang'e-5 probe with the orbiter-returner combination at Beijing Aerospace Control Center in Beijing on Dec 6, 2020. (Photo: Xinhua)

A man receives the COVID-19 vaccine injection in Moscow, Russia, on Dec 5, 2020. Moscow mayor Sergei Sobyanin announced Friday that the Russian capital city has launched its mass immunization program against the coronavirus. (Photo: CFP)

A bronze horse head sculpture looted from Yuanmingyuan is on display at Wenshu Pavilion of Zhengjue Temple in Yuanmingyuan, Beijing, Dec 1, 2020. A bronze horse head sculpture, a treasure of China's Old Summer Palace that went missing after an Anglo-French allied forces' looting 160 years ago, returned to its original palace home Tuesday. (Photo: Xinhua)

Two children stand in front of a light installations called Moongarden at the Stavros Niarchos Foundation Cultural Center, in Athens, Greece, Dec 2, 2020. (Photo: AP)

Photo of the Chinese quantum computer shows the process of light-based quantum interference. The University of Science and Technology of China announced on Dec 4, 2020, that its research team had established a quantum computer prototype, named “Jiuzhang,” through which up to 76 photons were detected. (Photo: Xinhua)

Jessica Walker and Nicola Foster, known as the Lido Ladies, swim at the Charlton Lido in Hornfair Park on its first day of reopening after the second national lockdown ended and England enters a strengthened tiered system of regional coronavirus restrictions, in London, Britain, Dec 2, 2020. (Photo: CFP)

A fisherman pulls his fishing net in a lake in Ajmer, Rajasthan, India, on Dec 4, 2020. (Photo: CFP)

The Seventeen Hole Bridge on Kunming Lake in the Summer Palace, also known as Yiheyuan, is seen at sunset in Beijing, on Nov 30, 2020. (Photo: SIPA)

A bomb-sniffing dog is seen with members of the K9 unit of the Philippine Coast Guard (PCG) during a bomb threat and hostage-taking response capability exercise at a pier in Manila, the Philippines, Dec 1, 2020. (Photo: Xinhua)