A pro and con paragraph has been written about hydrogen-powered cars. The paragraph has been broken into a list of sentences and pairs of sentences. Try to find the sentences that support the positive aspects of the topic (the "pro" sentences). Select the "pro" sentences.

A. The potential for hydrogen-powered cars to change our energy habits is compelling.
B. However, significant problems may lessen their impact.
C. Compared to the standard gasoline engine, hydrogen cars are non-polluting. The principal by-product of gas engines is carbon dioxide, the major contributor to air pollution.
D. Hydrogen cars expel water vapor rather than carbon dioxide into the atmosphere. In cities, this technology could be key to cleaning up air polluted by automobiles.
E. There are, however, a number of challenges that may reduce the impact of hydrogen technology.
F. Industry analysts project that it would take 15 to 20 years for hydrogen cars to permeate the marketplace enough to result in a measurable reduction in pollution.
G. An entirely new infrastructure will be required to service these autos.
H. Some critics charge that proposed government investment of several hundred million dollars in hydrogen technology will have little impact on reducing air pollution and foreign oil dependence.
I. Hybrid gas/electric vehicles that achieve 40 miles per gallon or more may have a greater short-term impact on the environment.
J. Though it presents an environment-friendly alternative to standard autos, complex issues surrounding the hydrogen car may limit its positive impact.