With Respect to the U

With respect to the U.S. transportation system, what best explains why electric motors are considered as the most sustainable means of running cars and trains in the future?

A) fuels for internal combustion engines all produce greenhouse gases
B) conventional crude oil will soon be in short supply
C) internal combustion engines are too inefficient for the expected growth in population
D) reserves of non-conventional fossil fuel are relatively small
E) electricity generated by nuclear power is expected to become significantly less expensive