Choose the two central ideas of the passage.
A. Cars have become safer, cleaner running, and faster over time.
B. The fastest cars are too expensive for the average person to buy.
C. The assembly line process made it possible for more people to buy cars,
D. People have used cars for both productivity and pleasure since the early 1900s.
E. Environmental concerns changed the way cars were designed and manufactured in the 1970s.
F. People need a clearer definition of "production car" and standard rules for certification before they can determine what is truly the fastest car.