The correct answer is A. burn.
Compressed natural gas (CNG) is a cleaner-burning alternative to gasoline. It produces fewer emissions, including carbon monoxide, hydrocarbons, and nitrogen oxides. CNG also has a higher octane rating than gasoline, which means it can be compressed more before it ignites. This makes it more efficient and can help to improve fuel economy.
However, CNG does not burn as efficiently as gasoline. This is because it has a lower energy density. This means that it takes more CNG to produce the same amount of power as gasoline. As a result, CNG vehicles typically have a lower range than gasoline-powered vehicles.
Overall, CNG is a cleaner-burning alternative to gasoline that can help to improve fuel economy. However, it does not burn as efficiently as gasoline, which means that CNG vehicles typically have a lower range.
Option B, “burns,” is incorrect because it is not a complete sentence. Option C, “should burn,” is incorrect because it is not a fact. Option D, “none of these,” is incorrect because the correct answer is “burn.”