Which of me following best completes the passage below?

Which of me following best completes the passage below?

Adding ethanol to the gasoline used in cars reduces exhaust emissions while slightly increasing evaporation from gasoline tanks in cars and service stations. These evaporative emissions are a major component of the smog found in many large cities in the hot summer months but, except in hot weather, evaporative emissions pose less of a pollution problem than exhaust emissions do. Therefore, if air pollution were the only consideration, one could conclude that -----.
(A) ethanol should be added only to gasoline intended for use in large cities
(B) the benefits of using gasoline to which ethanol has been added are greater in hot weather than in cold weather
(C) the disadvantages of adding ethanol to gasoline are likely to be outweighed by the advantages, at least in cold weather
(D) it is not necessary to work at reducing exhaust emissions in large cities
(E) adding ethanol to the gasoline used in large cities will improve air quality in the cities in hot weather