The cracking method used to obtain better quality gasoline is:

Explanation

The correct answer is Catalytic cracking, which is a preferred method for producing higher quality gasoline. This process employs catalysts to facilitate the breakdown of larger hydrocarbon molecules into smaller, more valuable ones, enhancing the quality of the final product. In contrast, Thermal cracking generates lower quality fuels due to the absence of catalysts and the harsh conditions involved. Steam cracking, while effective for producing lighter hydrocarbons, does not specifically aim to improve gasoline production. Radiations do not play a significant role in the cracking processes used in the petroleum industry.