GWD5/24 的一道题。请教

GWD7-Q14:
Certain politiciansin the country of Birangi argue that a 50 percent tax on new automobiles wouldhalt the rapid increase of automobiles on Birangi’s roads and thereby slow thedeterioration of Birangi’s air quality. Although most experts agree that such a tax would result in fewerBirangians buying new vehicles and gradually reduce the number of automobileson Birangi’s roads, they contend that it would have little impact on Birangi’sair-quality problem.
Which of thefollowing, if true in Birangi, would most strongly support the experts’contention about the effect of the proposed automobile tax on Birangi’sair-quality problem?
A. Automobileemissions are the largest single source of air pollution.
B. Someof the proceeds from the new tax would go toward expanding the nonpollutingcommuter rail system.
C. Currently,the sales tax on new automobiles is considerably lower than 50 percent.
D. Automobilesbecome less fuel efficient and therefore contribute more to air pollution asthey age.
E. Thescrapping of automobiles causes insignificant amounts of air pollution.
怎么看都没有正确答案啊。。。