How much is the percent of air transportation in all modes?（）

A.The high value     
B.Low density or weight
C.A and B           
D.Shortest time to transport

A.Quick but not safe        
B.Less frequency
C.It can’t lift heavy goods    
D.The highest cost in all transport modes

A.Near way      
B.The distance is not long   
C.Direct line     
D.Short road