The assembly line was a system through which items were mass-produced in a continuous flow.
What is the assembly line?
The assembly line was a measure used by manufacturing companies in America in the early 1900s for the purpose of producing goods on large scales. The items manufactured in mass quantities included vehicles, clothes, and automobile spare parts.
These assembly lines comprised items that were mass-produced in a continuous flow. It enabled workers to complete their tasks faster and made the cost of production cheaper. So, the correct word for the blank space is continuous.