Students review history of PLA Navy at science class in Qingdao, China's Shandong

Students learn about flag semaphore during a science class at Jiayuguan school in Qingdao, east China's Shandong Province, April 22, 2019. Teachers and students here reviewed the history of the People's Liberation Army (PLA) Navy and learned the knowledge about vessels and oceans upon PLA Navy's 70th founding anniversary. (Xinhua/Li Ziheng)