The first mistake is the use of the word "less" when used with the noun "cars." Instead, the correct word should be "fewer." In general, use the word "fewer" when the number of objects can be counted; use the word "less" when the objects cannot be counted. For example: fewer cars on the road (cars can be counted), but less traffic (traffic is a general noun and cannot be counted).
Also, note that the verb "means" does not agree with the subject "cars." Therefore, the correct sentence should read: Fewer cars on the road mean less traffic.</span>
If you mean which sentance best represents the moral of the story then it would be the second to last sentence: "At last a Wolf really did come, and the Boy cried, "Wolf! wolf!" as loud as he could: but the people were so used to hearing him call that they took no notice of his cries for help."
