IPOGeely-backed service seeks to challenge market leader DidiCaoCao listed at a price 19% lower than its public offering price. (Photo by Kensaku Ihara)HONG KONG -- Chinese ride-hailing service CaoCao listed on the Hong Kong Stock Exchange on Wednesday, raising 1.85 billion Hong Kong dollars ($236 million) to help fund its efforts to take on Didi, which commands the national market.The company, a division of privately owned Chinese automaker Geely, listed at a price 19% lower than its public off...