Ahh, the 1920's. This is when the US started to rise to the top. The assembly line is what had everyone building things in large amounts. Here's an example.
ok there are 5 people, each of us has a letter .
Person 1: A - He gives a to person 2
Person 2: p - puts Ap together and passes it to person 3.
Person 3: p - Puts it together and gets App passes it to person 4
Person 4: l - Adds it to the App to get Appl, then gives to person 5.
Person 5: e - Puts the finishing touch on the project and there finale thing is...
Apple!!! Do you get it now?
Hope I helped. :)
Answer:
C. Introduction of the assembly line.
Explanation: