Have you ever imagined what kind of car we will be driving in 2020? It will be rather different from the type we know today, with the next 20 years bringing greater change than the past 50. The people who will be designing the models of tomorrow believe that environmental problems may well accelerate(,)the pace of the car's development. Today they are students on the transport design course at London's Royal College of Art. Their vision is of a machine with three wheels instead of four, electrically powered, environmentally clean, and able to drive itself along "intelligent" roads equipped with built-in power supplies. Future cars will pick up their fuel during long journeys from a power source built into the road, or store it in small quantities for traveling in the city. Instead of today's seating arrangements--two in front, two or three behind, all facing forward--the 2010 car will have a versatile interior with adults and children in a family circle. This view of the future car is based on a much more sophisticated road system,  _ Cars will not need drivers, because computers will provide safe driving control and route finding. All the driver will have to do is to say where to go and the computer will do the rest. It will become impossible for cars to crash into one another. The technology already exists for the car to become a true automobile. A future car will use electrical power, because it is  _  .
safer cheaper cleaner faster
Question: Have you ever imagined what kind of car we will be driving in 2020? It will be rather different from the type we know today, with the next 20 years bringing greater change than the past 50. The people who will be designing the models of tomorrow believe that environmental problems may well accelerate(,)the pace of the car's development. Today they are students on the transport design course at London's Royal College of Art. Their vision is of a machine with three wheels instead of four, electrically powered, environmentally clean, and able to drive itself along "intelligent" roads equipped with built-in power supplies. Future cars will pick up their fuel during long journeys from a power source built into the road, or store it in small quantities for traveling in the city. Instead of today's seating arrangements--two in front, two or three behind, all facing forward--the 2010 car will have a versatile interior with adults and children in a family circle. This view of the future car is based on a much more sophisticated road system,  _ Cars will not need drivers, because computers will provide safe driving control and route finding. All the driver will have to do is to say where to go and the computer will do the rest. It will become impossible for cars to crash into one another. The technology already exists for the car to become a true automobile. A future car will use electrical power, because it is  _  .
A. safer
B. cheaper
C. cleaner
D. faster
Answer: