Correct option is A. Detroit
One important feature of the US economy of the 1920swas mass production. The move towards mass production had begun in the late nineteenth century, but in the 1920s it became a characteristic feature of industrial production in the US. A well-known pioneer of mass production was the car manufacturer Henry Ford. He adapted the assembly line of a Chicago slaughterhouse (in which slaughtered animals were picked apart by butchers as they came down a conveyor belt) to his new car plant in Detroit. He realised that the assembly line method would allow a faster and cheaper way of producing vehicles. The assembly line forced workers to repeat a single task mechanically and continuously such as fitting a particular part to the car at a pace dictated by the conveyor belt. This was a way of increasing the output per worker by speeding up the pace of work. Standing in front of a conveyor belt no worker could afford to delay the motions, take a break, or even have a friendly word with a workmate. As a result, Henry Fords cars came off the assembly line at three-minute intervals, as peed much faster than that achieved by previous methods. The T Model Ford was the worlds first mass-produced car.