6.2 Video 1. 电动集装箱运输 http://yzkc.scetop.com/gjmy/wp-content/uploads/sites/20/2021/07/电动集装箱运输.mp4 2. 集装箱的尺寸 http://yzkc.scetop.com/gjmy/wp-content/uploads/sites/20/2021/07/集装箱的尺寸-.mp4 3. 背书是什么? http://yzkc.scetop.com/gjmy/wp-content/uploads/sites/20/2021/07/背书是什么?.mp4