单项选择题
A. the meteor sonic boom. B. atmospheric impact of a small asteroid. C. an asteroid zooming close by the Earth. D. flying glass.
A. Car crash. B. Heavy snow and ice. C. Truck rollover on highway. D. Train derailment.
A. achieve cleaner, more energy-efficient modes of transportation. B. reduce the energy intensity of economic activities. C. reach the goal of reducing transportation cost. D. promote the use of fossil fuels.