Of the two choices, none of those people invented the assembly line. I believe you are thinking of Henry Ford who was the first to start using a moving assembly line. The concept of an assembly was to speed production and to divide labor. A worker on the assembly line does one specific job in the manufacturing process, over and over each day. By doing only one part of the job and having others do another part of the job, manufacturing can be done faster.
It should be noted that Henry Ford was the first to use the moving assembly line. Ransom Olds invented the first assembly line. He used the assembly to manufacture cars. His assembly line also increased the rate of production of automobiles.
Thus, in your question, I believe you are referring to Henry Ford. It should be noted that Henry Ford invented the first moving assembly line while Ransom Olds invented the first assembly line.