▲閱讀下文，回答第 39－41 題
      Imagine getting into your car, speaking a location into your car’s computer, and then
letting it drive you to your destination. The idea behind self-driving cars is fairly simple: build
a car with a computer that is connected with many cameras which can track all the objects close
to it, give the computer all the driving rules and routes, and then the computer should be able to
drive to the destination.
      There are many benefits of self-driving cars. Research shows that using self-driving cars
can greatly reduce the number of cars on the street because 80 % only have one person driving
alone in a car. Self-driving cars can also lower the cost of transportation, which is 18 % of a
person's income in the U.S.A. Besides, “These cars won't get drunk, drive too fast, or take
risks,” said the CEO of Fastcar, John Smith.
      Early estimates suggested that self-driving cars would be the standard in 2020, but instead
there were only a few research vehicles on the road in 2020. As the technology is currently
under research and being improved, it is likely in the near future that we will see self-driving
cars move safely on public roads among traditional cars. When they arrive, their cost, safety
and convenience will make them part of our daily lives. Companies that research self-driving
cars which plan ahead, adjust the quickest, and imagine the most will succeed.
【題組】39. What is the main idea of this article?
(A) Setting up self-driving car companies
(B) Driving rules for self-driving cars
(C) The costing of self-driving cars
(D) The coming of self-driving cars