Here are little cars that may some day take the place of today’s cars. If everyone drives such a car in the future, there will be less pollution in the air. There will also be more parking spaces in cities, and the streets will be less crowded. Three such Cars fit in the space now needed for one Car of the usual size. The little cars will cost much less to own and to drive. Driving will be safer, too, as these little cars can go only 55 miles per hour. The Cars of the future will be fine for getting around a city, but they will not be useful for long trips.

What’s about the cost of owning and driving such cars
The little cars will cost（）to own and to drive.

某校科技节上，老师将液氮“倒”在装有超导物质的磁悬浮列车模型上，由于液氮迅速汽化并　    　热量，超导物质降温后变为超导体，使模型能悬浮在通电的环形轨道上．当模型在环形轨道上运行时，其运动状态　    　（填“改变”或“不变”）．