Passengers have their tickets checked before taking a train of subway line No. 3 in Qingdao, east China's Shandong Province, Dec. 16, 2015. The north section of Qingdao Subway Line No. 3, the first subway line of Shandong, was put into operation on Wednesday. Travel time of the 12-kilometer-long line is about 19 minutes. [Photo/Xinhua]