Which letters are omitted in UTC identifiers to avoid confusion with numbers?

Which letters are omitted in UTC identifiers to avoid confusion with numbers?

• A. I and J
• B. O and Q
• C. Q and Z
• D. I and O

Answer: (D)

When identifiers mix letters and numbers, removing letters that can look like digits helps prevent misreads. The two letters left out are I and O because I can resemble 1 and O can resemble 0 in many fonts and handwriting. Dropping these two makes UTC identifiers clearer when read or transcribed, reducing errors. Other letters don’t create the same confusion with digits, so omitting them wouldn’t address the readability issue in the same way.

When identifiers mix letters and numbers, removing letters that can look like digits helps prevent misreads. The two letters left out are I and O because I can resemble 1 and O can resemble 0 in many fonts and handwriting. Dropping these two makes UTC identifiers clearer when read or transcribed, reducing errors. Other letters don’t create the same confusion with digits, so omitting them wouldn’t address the readability issue in the same way.