Team Strong Silvers member Ngai Hin Kwok, 66, works out as teammate Ng Siu Chi, 57, watches at a stadium in Singapore March 15, 2015. Team Strong Silvers, is a group of senior citizens who train in calisthenics. The trio trains individually at least three times a week, and meets up for joint calisthenics at least twice a month. (Photo by Edgar Su/Reuters)

In this November 28, 1966 file photo, one of the 10 beagles involved in the first test of the Veterans Administration Hospital in East Orange, N.J. smokes a cigarette through a machine linked to its windpipe by a plastic tube to test any link between smoking and emphysema. (Photo by AP Photo)

A Chinese rescuer evacuates a young boy from flooded areas caused by heavy rains in Changsha city, central China's Hunan provincehangsha, capital of Hunan on July 3, 2017. (Photo by Imaginechina/Rex Features/Shutterstock)

American fashion model Simone Thompson, better known as Slick Woods walks at the Savage x Fenty – September 2018 – New York Fashion Week at Brooklyn Navy Yard on September 12, 2018 in Brooklyn, New York. (Photo by Presley Ann/Patrick McMullan via Getty Images)

A silkmoth that has hatched out of its cocoon is seen at the Campoverde cooperative, Castelfranco Veneto, Italy June 4, 2015. Despite having wings, the adult moth cannot fly. Clusters of silkworms munch on piles of locally-grown mulberry leaves in a white marquee in Italy's northern Veneto region. They are nourishing hopes of a revival of Italy's 1,000 year-old silk industry. (Photo by Alessandro Bianchi/Reuters)

A train attendant helps a passenger to adjust her seat at the business class carriage on a CRH 380A bullet train Thursday, June 16, 2011. (Photo by Reuters/China Daily)

U.S. Democratic presidential candidate Hillary Clinton takes a photo with supporters John Nelson, 32, (L) and Dan Stifler, 32, (C) after speaking at the UFCW Union Local 324 in Buena Park, California, U.S. May 25, 2016. (Photo by Lucy Nicholson/Reuters)

An artist wearing a coronavirus-shaped helmet and a protective suit stands next to a police barricade as he requests people to stay at home during an extended lockdown to slow the spread of the coronavirus disease (COVID-19) in New Delhi, India, April 30, 2020. (Photo by Adnan Abidi/Reuters)