The correct answer is (a). Alcohol has better anti-knock characteristics than gasoline. This means that it is less likely to cause engine knocking, which can damage the engine. Alcohol is a better fuel for engines because it has a higher octane rating than gasoline. Octane rating is a measure of a fuel’s resistance to knocking. The higher the octane rating, the less likely the fuel is to knock. Alcohol also has a higher energy content than gasoline, which means that it can produce more power.
Option (b) is incorrect because alcohol does not have poor anti-knock characteristics. In fact, it has better anti-knock characteristics than gasoline.
Option (c) is incorrect because alcohol is not the same as gasoline. It has different properties, including a higher octane rating and a higher energy content.
Option (d) is incorrect because alcohol’s anti-knock characteristics do not keep changing. They are always better than gasoline’s.