What is the 13-character number assigned by an activity for its own use?

The correct answer is Local Item Control Number. This term refers to the specific 13-character identifier that is assigned by individual activities for use in managing their inventory and logistical operations. The purpose of this number is to facilitate local tracking and control of items within an organization's supply chain, allowing for more efficient inventory management and accountability at the local level.

In contrast, the other options pertain to identifiers used at different levels or for different specific purposes within supply chain management. The Navy Item Control Number is a standardized number for items recognized across the Navy and used for inventory management at a broader scale. The Procurement Control Number typically relates to processes involved in the acquisition of goods and services, serving a distinct function in purchasing operations. The Supply Chain Identifier, while it may relate to tracking items throughout a supply chain, does not specifically refer to a localized number utilized by an activity for its independent use. Thus, the Local Item Control Number is specifically tailored for local inventory management, making it the correct choice in this context.