Which MARC tag is associated with physical description of a resource?

The correct association for the physical description of a resource in the MARC (Machine-Readable Cataloging) format is tagged as 300. This tag specifically provides details about the physical characteristics of the item being cataloged, such as its dimensions, number of pages, illustrations, or other relevant physical attributes. Understanding this tag is crucial for librarians as it helps in accurately representing the physical aspects of resources in a library catalog, allowing users to discern the nature of the item they are interested in.

In contrast, the other tags mentioned serve different purposes: the 245 tag is used for the title statement, including the title and statement of responsibility; the 650 tag is for subject added entries; and the 900 tag is for local use, often containing information specific to a particular library’s cataloging practices. Each of these serves an important function but does not pertain to the physical description in the same way the 300 tag does.