GWD7-Q14答案是不是有问题啊？

Q14:
Certain politicians in the country of Birangi argue that a 50 percent tax on new automobiles would halt the rapid increase of automobiles on Birangi’s roads and thereby slow the deterioration of Birangi’s air quality.  Although most experts agree that such a tax would result in fewer Birangians buying new vehicles and gradually reduce the number of automobiles on Birangi’s roads, they contend that it would have little impact on Birangi’s air-quality problem.

Which of the following, if true in Birangi, would most strongly support the experts’ contention about the effect of the proposed automobile tax on Birangi’s air-quality problem?

A. Automobile emissions are the largest single source of air pollution.
B. Some of the proceeds from the new tax would go toward expanding the nonpolluting commuter rail system.
C. Currently, the sales tax on new automobiles is considerably lower than 50 percent.
D. Automobiles become less fuel efficient and therefore contribute more to air pollution as they age.
E. The scrapping of automobiles causes insignificant amounts of air pollution.

这道题答案是D，我怎么觉得E正确？各位都是怎么选的？