試題詳解

33. Because the supply of natural gas was plentiful in comparison to other choices like coal and fuel oil, and because it burns cleaner, many people changed their heating systems to natural gas, thereby creating shortages. Why did people prefer gas?
(A) It was natural.
(B) There were no other choices.
(C) The other fuels were dirtier and less plentiful.
(D) There is, even today, a plentiful supply of it.