The automobile industry affected life in the "roaring 20s" in all of the following ways except:
a. suburbs began to spring up, because many people could now drive to work.
b. the average household owned several cars.
c. other industries, like glass and rubber, developed.
d. people in the u. s. took more vacations.

The answer is B. 
In the days of early automobiles, it was unlikely that an average American household owned more than one car. The auto industry was somewhat of a monopoly, cars were expensive and made by one supplier, Ford automotive. 
Today, cars are more widely produced and even imported. They're more available to purchase. 

Millatary capacity build was higher level