China's Shang Chunsong prepares to compete in the uneven bars event of the women's individual all-around final artistic gymnastics competition at the Namdong Gymnasium Club during the 17th Asian Games in Incheon, in this September 23, 2014 file photo. (Photo by Kim Hong-Ji/Reuters)

Female Afghan National Police (ANP) officers aim their weapons during a drill at a training centre near the German Bundeswehr army camp Marmal in Mazar-e-Sharif, northern Afghanistan on December 11, 2012. (Photo by Fabrizio Bensch/Reuters/File Photo)

In this Thursday, June 14, 2018, file photo, students wear virtual reality goggles during a science class at Pyongyang Teachers' University, a teacher training college, in Pyongyang, North Korea. (Photo by Dita Alangkara/AP Photo)

In this Saturday, July 14, 2018, file photo, waves caused by high tide envelops a man standing outside his house near the Arabian Sea in Mumbai, India. The man was washed away by the wave and rescued by locals about 100 meters away from the spot. (Photo by Rajanish Kakade/AP Photo)

In this Sunday, March 24, 2019, file photo, free skate pairs gold medalist Sui Wenjing and Han Cong of China perform during the gala exhibition for the ISU World Figure Skating Championships at Saitama Super Arena in Saitama, north of Tokyo. (Photo by Annice Lyn/AP Photo)

In this October 27, 1983 file photo, soldiers brandish captured AK-47 rifles from the windows of a civilian vehicle as they drive near Point Salines Airport in St. George, Grenada. In 1983, U.S. forces invaded the Caribbean island of Grenada after accusing the government of allying itself with Communist Cuba. (Photo by Doug Jennings/AP Photo)

A model stands next to a BMW X6 AC Schnitzer car at Auto China 2012 in Beijing in this April 24, 2012 file photo. Amid the razzmatazz, music and crowds at the Shanghai autoshow on Monday, hundreds of attractive young women, and men, mingled among the stands and company booths, introducing the newest sedans and handing out pamphlets. For years, models have been a staple at China's big autoshows – as much of a draw as the latest car models themselves. 2015 is different – the organisers have banned models from the Shanghai show. (Photo by Jason Lee/Reuters)

In this October 15, 2014 file photo, Katsu Nakamura, sky division manager for Yamaha USA, moves the RMax unmanned helicopter into position before a demonstration of its aerial application capabilities at the University of California, Davis' Oakville Station test vineyard in Oakville, Calif. Researchers at UC Davis have been studying the effectiveness of the drone's ability for spraying pest control and nutritional materials on the test vineyard in California's Napa Valley. (Photo by Rich Pedroncelli/AP Photo)