Say no to PM2.5! (1/7)

A primary school student in Nanjing of Jiangsu province wears a mask with words making fun of smog under a clear sky on Dec 10, 2013. A primary school in Nanjing held an activity to call for low-carbon lifestyle for clean air. The city had been smothered by heavy smog for several consecutive days. [Photo: China News Service / Yang Bo]