Two students greet each other by touching elbows in a primary school in Guiyang, southwest China's Guizhou Province, May 25, 2020. Primary schools in Guiyang gradually resume classes. (Xinhua/Liu Xu)

A student dines at the canteen of a primary school in Guiyang, southwest China's Guizhou Province, May 25, 2020. Primary schools in Guiyang gradually resume classes. (Xinhua/Ou Dongqu)

A student helps her schoolmate to wear a mask in a primary school in Guiyang, southwest China's Guizhou Province, May 25, 2020. Primary schools in Guiyang gradually resume classes. (Xinhua/Ou Dongqu)

Students keep distance as they gather outdoors in a primary school in Guiyang, southwest China's Guizhou Province, May 25, 2020. Primary schools in Guiyang gradually resume classes. (Xinhua/Ou Dongqu)

A teacher squeezes disinfecting hand sanitizer for students in a primary school in Guiyang, southwest China's Guizhou Province, May 25, 2020. Primary schools in Guiyang gradually resume classes. (Xinhua/Ou Dongqu)

Students keep distance as they gather indoors in a primary school in Guiyang, southwest China's Guizhou Province, May 25, 2020. Primary schools in Guiyang gradually resume classes. (Xinhua/Ou Dongqu)