单项选择题 （）are respectively the dominant transport mode in China and in the United States.

单项选择题 Since rail network is not as extensive as highway network in most countries and its limitation to fixed track facilities, as a result, railroads provide （） service.

单项选择题 In general, factors influencing transportation costs can be grouped into 2 major categories---product-related factors and market-related factors. Please find below, （）is not belong to the market-related factors.