A farmer airs sliced sweet potato in Nishankou Village, Shuiquan Township of Zaozhuang City, east China's Shandong Province, Jan. 10, 2019. Taking the advantage of sunny days recently, farmers in Shuiquan Township are busy drying sliced sweet potatoes, a popular snack in northern China. (Xinhua/Liu Mingxiang)

　　A farmer airs sliced sweet potato in Nishankou Village, Shuiquan Township of Zaozhuang City, east China's Shandong Province, Jan. 10, 2019. Taking the advantage of sunny days recently, farmers in Shuiquan Township are busy drying sliced sweet potatoes, a popular snack in northern China. (Xinhua/Liu Mingxiang)

　　A farmer airs sliced sweet potato in Nishankou Village, Shuiquan Township of Zaozhuang City, east China's Shandong Province, Jan. 10, 2019. Taking the advantage of sunny days recently, farmers in Shuiquan Township are busy drying sliced sweet potatoes, a popular snack in northern China. (Xinhua/Liu Mingxiang)

　　A farmer airs sliced sweet potato in Nishankou Village, Shuiquan Township of Zaozhuang City, east China's Shandong Province, Jan. 10, 2019. Taking the advantage of sunny days recently, farmers in Shuiquan Township are busy drying sliced sweet potatoes, a popular snack in northern China. (Xinhua/Liu Mingxiang)