单项选择题
what kind of products do the air carriers deliver? （）
A. The high value B. Low density or weight C. A and B D. Shortest time to transport
单项选择题 What is the disadvantage for air transportation? （）
单项选择题 Loss and damage ration for motor are lower than any other modes. Is it correct?（）
单项选择题 The international trade needs the （） to fulfill its transaction.
