Answer: A demand-pull system in which each component in a production line is produced immediately as needed by the next step in the production line is referred to as: Just-in-time production or purchasing.
Explanation: The essence of Just In Time is that the supplies arrive at the factory, or the products to the customer, "just in time", that being shortly before they are used and only in the necessary quantities. This reduces or even eliminates the need for store and transfer the raw material from the warehouse to the production line (in the case of a factory).