With more and more cars running on the roads and the worsening air quality, many people begin to turn to clean fuels. What can car makers do to develop the technology of using clean fuels? Now listen to a news report and choose the best answer to each of the questions you hear.
选项：

A: The technology of hydrogen fuel-cell cars is not perfect.
B:Hydrogen fuel-cell cars are not 100 percent safe to drive.
C:There are not enough hydrogen fueling stations.
D:Hydrogen fuel-cell cars are too expensive for consumers to buy.