单项选择题

Directions: There are 10 questions in this part of the test. Read the passage through. Then, go back and choose one suitable word or phrase marked A, B, C, or D for each blank in the passage.
Assuming that a constant travel-time budget, geographic constraints and short-term infrastructure constraints persist as fundamental features of global mobility, what long-term results can one expect In high-income regions, 1 North America, our picture suggests that the share of traffic 2 Supplied by buses and automobiles will decline as high-speed transport rises sharply. In developing countries, we 3 the strongest increase to be in the shares first for buses and later for automobiles. Globally, these 4 in bus and automobile transport are partially offsetting. In all regions, the share of low-speed rail transport will probably continue its strongly 5 decline.
We expect that throughout the period 1990-2050, the average North American will continue to devote most of his or her 1.1-hour travel-time 6 to automobile travel. The very large demand for air travel (or high-speed rail travel) that will be manifest in 2050 7 to only 12 minutes per person a day; a little time goes a long way in the air. In several developing regions, most travel 8 in 2050 will still be devoted to nonmotorized modes. Buses will persist whatever it is the primary form of motorized transportation in developing countries for decades. 9 important air travel becomes, buses, automobiles and even low-speed trains will surely go on serving vital functions. 10 of the super-rich already commute and shop in aircraft, but average people will continue to spend most of their travel time on the ground.