Pupils draw a painting on environment protection at a primary school in Hohhot, capital of north China's Inner Mongolia Autonomous Region, June 5, 2017. Monday marks the World Environment Day, on which various activities are held across China to call for environment protection. (Xinhua/Ding Genhou)

A mascot for environment interacts with visitor at a scenic spot in Zhangjiajie, central China's Hunan Province, June 5, 2017. Monday marks the World Environment Day, on which various activities are held across China to call for environment protection. (Xinhua/Wu Yongbin)

Pupils draw a painting on environment protection at a primary school in Hohhot, capital of north China's Inner Mongolia Autonomous Region, June 5, 2017. Monday marks the World Environment Day, on which various activities are held across China to call for environment protection. (Xinhua/Ding Genhou)

Mascots for environment interact with visitor at a scenic spot in Zhangjiajie, central China's Hunan Province, June 5, 2017. Monday marks the World Environment Day, on which various activities are held across China to call for environment protection. (Xinhua/Wu Yongbin)

A mascot for environment interacts with visitor at a scenic spot in Zhangjiajie, central China's Hunan Province, June 5, 2017. Monday marks the World Environment Day, on which various activities are held across China to call for environment protection. (Xinhua/Wu Yongbin)

Children draw a painting about a green world at a kindergarten in Huzhou City, east China's Zhejiang Province, June 5, 2017. Monday marks the World Environment Day, on which various activities are held across China to call for environment protection. (Xinhua/Xu Yu)

Volunteers introduce garbage classification to children at a kindergarten in Huzhou City, east China's Zhejiang Province, June 5, 2017. Monday marks the World Environment Day, on which various activities are held across China to call for environment protection. (Xinhua/Xu Yu)

A pupil chants poem during an environmental protection activity at a primary school in Hangzhou, capital of east China's Zhejiang Province, June 5, 2017. Monday marks the World Environment Day, on which various activities are held across China to call for environment protection. (Xinhua/Zhang Cheng)

Pupils perform during an environmental protection activity at a primary school in Hangzhou, capital of east China's Zhejiang Province, June 5, 2017. Monday marks the World Environment Day, on which various activities are held across China to call for environment protection. (Xinhua/Zhang Cheng)

Pupils visit a water-quality monitor car during an environmental protection activity at a primary school in Hangzhou, capital of east China's Zhejiang Province, June 5, 2017. Monday marks the World Environment Day, on which various activities are held across China to call for environment protection. (Xinhua/Zhang Cheng)

A staff member shows an air monitoring equipment to citizens during an open day activity at the environmental monitoring center in Dalian, northeast China's Liaoning Province, June 5, 2017. Monday marks the World Environment Day, on which various activities are held across China to call for environment protection. (Xinhua/Zhang Chunlei)