Step 1: Understanding the Question
The question asks for the standard dimensions of a traditional library catalog card, expressed in centimeters.
Step 2: Key Formula or Approach
This is a standard measurement in traditional librarianship. The approach is to recall this standard size, which is recognized internationally. The size is also commonly expressed in inches.
Step 3: Detailed Explanation
The catalog card was the primary tool for library catalogs before the advent of computers. Its size was standardized to ensure interchangeability and fit into standard catalog drawers.
The internationally accepted standard size is 12.5 cm in width and 7.5 cm in height.
This corresponds to approximately 5 inches by 3 inches.
Step 4: Final Answer
The standard size of a physical catalog card is 12.5 cm $\times$ 7.5 cm. Therefore, Option (B) is the correct answer.