Final answer:
Control of monetary flows represents the most routine, day-to-day supply chain activity, unlike the other options that involve less frequent strategic or planning decisions.
Step-by-step explanation:
The most day-to-day, routine activity among the options provided is D. control of monetary flows. This activity involves the day-to-day management of financial transactions that support the operations of a business. Tasks include managing the inflow and outflow of cash, ensuring that suppliers are paid on time, and that customers are invoicing correctly. This contrasts with the less frequent activities such as workforce leveling, which relates to human resource management strategies, warehouse location determination, which is typically a strategic decision made infrequently, and capacity decision making, which often involves long-term planning and investment.