A cost-effective solution to the problem of airport congestion is to provide high-speed ground transportation between major cities lying 200 to 500 miles apart. The successful implementation of this plan would cost far less than expanding existing airports and would also reduce the number of airplanes clogging both airports and airways. Which of the following, if true, could proponents of the plan above most appropriately cite as a piece of evidence for the soundness of their plan？

An effective high-speed ground-transportation system would require major repairs to many highways and mass-transit improvements.
B. One-half of all departing flights in the nation"s busiest airport head for a destination in a major city 225 miles away.
C. The majority of travelers departing from rural airports are flying to destinations in cities over 600 miles away.
D. Many new airports are being built in areas that are presently served by high-speed ground-transportation systems.
E. A large proportion of air travelers are vacationers who are taking long-distance flights.