单项选择题
（）is the disadvantage for air transportation?
A. Quick but not safe B. Less frequency C. It can’t lift heavy goods D. the highest cost in all transport modes
单项选择题 What is the meaning of “short hauls”? （）
单项选择题 Motor transport has the biggest market share in the paragraph. Is it true or not （）
单项选择题 How long is the economic distance for motor? （）
