People in several American states may be surprised to see cars on city streets without a driver. Experimental driverless vehicles now are legal in Florida, Nevada and California. They are pointing the way to a future that is not far down the road. The high-tech company Google has a number of self-driving cars, which had covered 480,000 kilometers by August. Volvo is among the companies doing road tests and says it plans to sell driverless cars by 2020.      In September, California Governor Jerry Brown signed an act to allow autonomous vehicles on the roads of his state.  " Today we're looking at science fiction becoming tomorrow's reality-the driverless car. " The technology for these cars includes cameras, radar and motion sensors. The systems have been improved through competitions sponsored by the U. S. government agency DARPA. Engineer Richard Mason of the Rand Corporation helped design driverless vehicles for DARPA challenge races.      Cars have become much more fuel-efficient, and new electronic features are' making Hondas safer,  said Angie Nucci of Honda America.  " A camera on the passenger-side mirror actually engaged on your guiding screen so you can safely change lanes. " Other safety features include warning systems on the front and the sides of the cars.  These systems help drivers ,  but don't replace them. Curator Leslie Kendall of the Petersen Automotive Museum said autonomous cars will make the high ways safer.      "By taking out drivers, you also remove most risks of an accident," Kendall said. He said consumers, however, may be unwilling to lose control. "It may take them time to come to realize that the technology is indeed reliable, but it will have to prove itself first. "      Mason said the technology already works and the biggest challenge now is getting down the cost for driverless vehicles from hundreds of thousands of dollars to something more affordable. He said this will happen as the technology is improved. ks5u According to Richard Mason, what is the biggest challenge for driverless cars?
They are not allowed to run on the road. Their technical problems remain to be solved. They are now too expensive for consumers. They are more dangerous for people on the street.
Question: People in several American states may be surprised to see cars on city streets without a driver. Experimental driverless vehicles now are legal in Florida, Nevada and California. They are pointing the way to a future that is not far down the road. The high-tech company Google has a number of self-driving cars, which had covered 480,000 kilometers by August. Volvo is among the companies doing road tests and says it plans to sell driverless cars by 2020.      In September, California Governor Jerry Brown signed an act to allow autonomous vehicles on the roads of his state.  " Today we're looking at science fiction becoming tomorrow's reality-the driverless car. " The technology for these cars includes cameras, radar and motion sensors. The systems have been improved through competitions sponsored by the U. S. government agency DARPA. Engineer Richard Mason of the Rand Corporation helped design driverless vehicles for DARPA challenge races.      Cars have become much more fuel-efficient, and new electronic features are' making Hondas safer,  said Angie Nucci of Honda America.  " A camera on the passenger-side mirror actually engaged on your guiding screen so you can safely change lanes. " Other safety features include warning systems on the front and the sides of the cars.  These systems help drivers ,  but don't replace them. Curator Leslie Kendall of the Petersen Automotive Museum said autonomous cars will make the high ways safer.      "By taking out drivers, you also remove most risks of an accident," Kendall said. He said consumers, however, may be unwilling to lose control. "It may take them time to come to realize that the technology is indeed reliable, but it will have to prove itself first. "      Mason said the technology already works and the biggest challenge now is getting down the cost for driverless vehicles from hundreds of thousands of dollars to something more affordable. He said this will happen as the technology is improved. ks5u According to Richard Mason, what is the biggest challenge for driverless cars?
A. They are not allowed to run on the road.
B. Their technical problems remain to be solved.
C. They are now too expensive for consumers.
D. They are more dangerous for people on the street.
Answer: