A staff member from a water ecology management service provider shows visitors how to test drinking water quality using a block-chain-based management and control system at the 2nd Digital China Exhibition in Fuzhou, southeast China's Fujian Province, May 5, 2019. The 2nd Digital China Exhibition runs from May 5 to 9 at the Fuzhou Strait International Conference & Exhibition Center. (Xinhua/Wei Peiquan)