Which is the best analogy for classification?

Classification is the act of grouping things by shared qualities or characteristics. 
With your given options to the most accurate analogy would be the organization of clothes based on type, color and season. 
Alphabetizing implies a specific order is necessary which with classification it is not. The car wash analogy is incorrect because those people were assigned specific traits (in this case their items/job) but when classifying you do not assign any trait, you sort them as is.

Hope I helped.

Generally travels west to east but often shifts to north and south