Which statement about check digits is true?

• A. They provide an extra digit to help detect errors in a sequence.
• B. They guarantee data is always accurate.
• C. They validate the data length.
• D. They confirm the data matches a required pattern.

Answer: (A)

Check digits are extra digits added to a numeric sequence, calculated from the other digits to help detect errors during entry or transmission. Because the check digit is tied to the rest of the data, mistakes like typing a wrong digit or swapping adjacent digits often lead to a mismatch that can be detected, allowing the error to be flagged. They don’t guarantee that data is always accurate, since some errors can slip through or produce a valid combination depending on the algorithm. They also don’t specifically validate data length or enforce a required pattern, which are separate checks. So the statement that they provide an extra digit to help detect errors is the true description.