Question

What would BEST explain the increased totals for all cars made in the 1920s?

Answer 1

The answer to the question given is:
better mass production techniques

Better mass production techniques BEST explains the increased totals for all cars made in the 1920s. Henry Ford, together with General Motors and Chrysler emerging as the “Big Three” auto companies,  innovated mass-production techniques that became standard,   by the 1920s.