The correct answer is B) one at the time, by hand.
Before Henry Ford revolutionized the automobile industry, most cars were made one at the time, by hand.
As you can imagine, it was a long, tiring process and costly. Then, enters Henry Ford, who introduced the assembly line on December 1, 1913, and changed the way to fabricate an entire car. Ford consulted with Frederick Taylor -father of the scientific management- to implement the most efficient system of producing its "T Model." That is how he came up with his assembly line in the plant of Highland Park, Michigan.