Which statement best describes an effect of the U. S. automobile industry's growth during the 1920's

Mass production and the set of assembly lines.

Explanation:

Henry ford was a pioneer in the automobile industry in 1920's. His dream was to make an inexpensive car that almost anyone could afford.

For this purpose, Ford decided to apply to car manufacturing a method of mass production currently used in some other industries.

So, he set up an assembly line that runs through one end of the building to the other one. At first, each worker had to move along the place, as the line did not move, adding different parts to the car.

But after some improvents, Ford had the line itself move like a conveyor belt, and workers only stood on their place and only wait until they have to insert the part established in each work "station". Once the automobile reached the end of the line, the car was ready to be driven.