Students attend the fourth live class of the "Tiangong Class" series at a primary school in Qinhuangdao, north China's Hebei Province, Sept. 21, 2023. The fourth live class from China's space station was held on Thursday afternoon, delivered by the Shenzhou-16 astronauts Jing Haipeng, Zhu Yangzhu and Gui Haichao to students on Earth. (Photo by Cao Jianxiong/Xinhua)