A primary student shows her art works on a environment-friendly bag during a painting event to celebrate Children's Day and promote awareness of environment protection in southwest China's Chongqing Municipality, May 31, 2016. [Photo/Xinhua]

Primary students show their art works on environment-friendly bags during a painting event to celebrate Children's Day and promote awareness of environment protection in southwest China's Chongqing Municipality, May 31, 2016. [Photo/Xinhua]

Primary students paint on environment-friendly bags during a painting event to celebrate Children's Day and promote awareness of environment protection in southwest China's Chongqing Municipality, May 31, 2016. [Photo/Xinhua]

Primary students show their art works on environment-friendly bags during a painting event to celebrate Children's Day and promote awareness of environment protection in southwest China's Chongqing Municipality, May 31, 2016. [Photo/Xinhua]

Primary students paint on environment-friendly bags during a painting event to celebrate Children's Day and promote awareness of environment protection in southwest China's Chongqing Municipality, May 31, 2016. [Photo/Xinhua]

Kids play go game, known as Weiqi in Chinese, during a kindergarten event to celebrate the Children's Day in Lanzhou, capital of northwest China's Gansu Province, May 31, 2016. [Photo/Xinhua]

Kids play go game, known as Weiqi in Chinese, during a kindergarten event to celebrate the Children's Day in Lanzhou, capital of northwest China's Gansu Province, May 31, 2016. [Photo/Xinhua]

Pupils of primary schools perform group callisthenics of hand-and-arm signals for traffic during an event to celebrate the Children's Day in Beijing, capital of China, May 31, 2016. [Photo/Xinhua]

Pupils of primary schools perform group callisthenics of hand-and-arm signals for traffic during an event to celebrate the Children's Day in Beijing, capital of China, May 31, 2016. [Photo/Xinhua] 

Pupils of primary schools perform group callisthenics of hand-and-arm signals for traffic during an event to celebrate the Children's Day in Beijing, capital of China, May 31, 2016. [Photo/Xinhua]

Pupils of primary schools perform group callisthenics of hand-and-arm signals for traffic during an event to celebrate the Children's Day in Beijing, capital of China, May 31, 2016. [Photo/Xinhua]

Students of Yudao School for children of migrant workers made chalkboard paints to express their wishes for the Children's Day in Hangzhou, capital of east China's Zhejiang Province, May 31, 2016. Zheng Fangwei, 13, wants to play basketball with his 11-year-old cousin who lives in Zheng's hometown. [Photo/Xinhua]

Students of Yudao School for children of migrant workers made chalkboard paints to express their wishes for the Children's Day in Hangzhou, capital of east China's Zhejiang Province, May 31, 2016. Zhu bingqian, 14, wants a teddy dog as a gift. [Photo/Xinhua]

Students of Yudao School for children of migrant workers made chalkboard paints to express their wishes for the Children's Day in Hangzhou, capital of east China's Zhejiang Province, May 31, 2016. Zuo Xiaofei, 10, wants to have a trip with her mother who is too busy to play with her. [Photo/Xinhua]

Students of Yudao School for children of migrant workers made chalkboard paints to express their wishes for the Children's Day in Hangzhou, capital of east China's Zhejiang Province, May 31, 2016. Li Fei, 13, wants to have a trip with her classmates. [Photo/Xinhua]

Students of Yudao School for children of migrant workers made chalkboard paints to express their wishes for the Children's Day in Hangzhou, capital of east China's Zhejiang Province, May 31, 2016. Zhang Daina, 12, wants to go to seaside with her family. [Photo/Xinhua]

Students of Yudao School for children of migrant workers made chalkboard paints to express their wishes for the Children's Day in Hangzhou, capital of east China's Zhejiang Province, May 31, 2016. Wu Shiya, 12, wants to pass a piano certificate test. [Photo/Xinhua]