The line of the article that supports the author's claim that cars helped to invent suburb is: "When the automobile became available to the masses, people were able to leave the cities to live."
The author goes on to explain the invention of the suburb related to cars in the line that says: "The automobile is what led to the growth and development of the suburbs".
Therefore, for the author, the suburbs were developed from the availability of automobiles to the masses, creating a new class system for Americans and enabling the mobility of people to places further away from the centers, creating the suburbs.
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