Protesters hold signs reading "Stop Tear Gas" during a rally against the police's use of tear gas in Hong Kong, Friday, Dec. 6, 2019. Hong Kong police have fired more than 10,000 tear gas canisters to quell violent protests that have rocked the city for six months. Its heavy and prolonged use in Hong Kong one of the world's most densely populated cities and known for its concrete jungle of high-rises is unusual and has sparked health fears. (AP Photo/Vincent Thian)