A Spanish national police officer uses his club to hit a protester during a demonstration called the Catalan pro-independence left youth group “Arran” on October 19, 2019 in Barcelona, a day after nearly 200 people were hurt in another night of violent clashes in Catalonia. The deterioration came on the fifth consecutive day of protests in the Catalan capital and elsewhere over a Spanish court's jailing of nine separatist leaders on sedition charges over a failed independence bid two years ago. (Photo by Josep Lago/AFP Photo)

Aerial photo taken on April 20, 2018 shows the view of advection fog above Qingdao, a coastal city in east China' s Shandong Province. (Photo by Lu Hui/Xinhua News Agency/Eyevine)

The Invasion. A quiet street in Macau. Modernization around is quickly changing the city, as documented by Paul Tsui. (Photo by Paul Tsui/National Geographic Travel Photographer of the Year Contest)

Long row of shiny new Flying Fortresses, part of huge reserves being built up in Britain for D-Day, stands by to be flown to combat units as replacements, May 25, 1944. (Photo by AP Photo)

Ballerinas perform during an ice-cream factory promotional event at an observation floor of the Moscow International Business Centre, also known as “Moskva-City”, in Moscow, Russia October 25, 2018. (Photo by Shamil Zhumatov/Reuters)

A man tries to extinguish an advertisement board set on fire during a demonstration of French labour union members and workers, as France faces its 38th consecutive day of strike against French government's pensions reform plans, in Paris, France on January 11, 2020. (Photo by Gonzalo Fuentes/Reuters)

A woman wearing a face mask as a precaution against the COVID-19 while using smartphone in a subway train in Hong Kong, Thursday, February 27, 2020. As the worst-hit areas of Asia continued to struggle with a viral epidemic, with hundreds more cases reported Thursday in South Korea and China, worries about infection and containment spread across the globe. (Photo by Kin Cheung/AP Photo)

An Iraqi medic takes a nasal swab from a woman in Iraq's central shrine city of Najaf on April 20, 2020, during the nationwide lockdown to stem the spread of the novel coronavirus. (Photo by Haidar Hamdani/AFP Photo)