Assuming that a constant travel-time budget, geographic constraints and short-term infrast

ructure constraints persist as fundamental features of global mobility, what long-term results can one expect7 In high-income regions, 【C1】______ North America, our picture suggests that the share of traffic 【C2】______ sup plied by buses and automobiles will decline as high-speed transport rises sharply. In developing countries, we 【C3】______ the strongest increase to be in the shares first for buses and later for automobiles. Glob ally, these 【C4】______ in bus and automobile transport are partially offsetting. In all regions, the share of low-speed rail transport will probably continue its strongly 【C5】______ decline.

We expect that throughout the period 1990—2050, the 【C6】______ North American will continue to de vote most of his or her 1. 1-hour travel-time 【C7】______ to automobile travel. The very large demand 【C8】______ air travel (or high-speed rail travel) that will be manifest in 2050 【C9】______ to only 12 minutes per person a day; a little time goes a long way in the air. In several developing regions, most travel 【C10】______ in 2050 will still be devoted to nonmotorized modes. Buses will persist 【C11】______ the primary form. of motorized transportation in developing countries for decades. 【C12】______ important air travel becomes, buses, automobiles and 【C13】______ low-speed trains will surely go on serving vital functions. 【C14】______ of the super-rich al ready commute and shop in aircraft, but average people will continue to spend most of their travel time on the 【C15】______.

【C1】______

A．frankly

B．exceptionally

C．unfortunately

D．notably