Final answer:
Engineer to order (ETO) requires the most collaboration between the manufacturer and customer, as products are custom-designed and produced to meet specific customer needs.
Step-by-step explanation:
The production strategy that requires the closest collaboration between the manufacturer and the customer is d. Engineer to order (ETO). In an ETO environment, products are designed and produced to customer specifications. This process often involves complex designs and customizations; therefore, there is a significant amount of interaction between the manufacturer and the customer to ensure that the final product meets the specific needs. The ETO approach contrasts with other strategies like make to stock (MTS), where items are produced for inventory based on predicted demand, and make to order (MTO) or assemble to order (ATO), where products are made or assembled once an order is received but are based on standard designs.
The trend of the design leading to a mechanized work environment does not typically apply to ETO, as ETO products are not identical and often require a more hands-on, customized approach to manufacturing.