Which characters are never used in a VIN?

The correct choice is the set of characters I, O, and Q. In the context of Vehicle Identification Numbers (VINs), these letters are excluded to prevent confusion with the numerals 1 and 0. Specifically, the letter "I" can easily be mistaken for the number 1, and both "O" and "Q" can be confused with the number 0. This practice is essential for ensuring clarity and accuracy in vehicle identification, which is crucial for various legal and regulatory processes.

The other letter combinations contain characters that are indeed part of VINs and do not serve a similar purpose of preventing potential misunderstandings or errors.