Which describes the allowed characters for the CSO code's third and fourth positions?

• A. Only letters.
• B. Any mixture of alpha/numeric excluding I and O.
• C. Only digits.
• D. Special characters allowed.

Answer: (B)

Third and fourth positions are designed to support a broad set of characters while minimizing confusion in reading or transcription. That means you can use both letters and numbers, but you exclude the letter I and the letter O to avoid confusion with the digits 1 and 0. Special characters are typically avoided in codes for system compatibility, so they wouldn’t be part of this allowed set. If you restricted to only letters or only digits, you’d severely limit the available combinations; including both letters and digits greatly increases possible codes. Excluding I and O keeps the code readable while preserving that larger space. So the description that fits best is a mixture of alphabetic and numeric characters, excluding I and O.