Children show greeting cards made to mark the World Hello Day which falls on Nov. 21 annually at a primary school in Hanshan District of Handan, north China's Hebei Province, Nov. 21, 2019. (Xinhua/Zhu Xudong)

Children say hello to each other during an activity to mark the World Hello Day which falls on Nov. 21 annually at a primary school in Hanshan District of Handan, north China's Hebei Province, Nov. 21, 2019. (Xinhua/Zhu Xudong)

Children show greeting cards made to mark the World Hello Day which falls on Nov. 21 annually at a primary school in Hanshan District of Handan, north China's Hebei Province, Nov. 21, 2019. (Xinhua/Zhu Xudong)

Children show greeting cards made to mark the World Hello Day which falls on Nov. 21 annually at a primary school in Hanshan District of Handan, north China's Hebei Province, Nov. 21, 2019. (Xinhua/Zhu Xudong)