To solve this question, the user needs to have a basic understanding of SAP R/3 user id parameters and the authorization levels for maintaining them.

Option A: Only the R/3 system administrator - This option is partially correct. The R/3 system administrator is authorized to maintain R/3 user id parameters, but there may be other users who are also authorized to do so.

Option B: Only the R/3 system administrator and the user - This option is partially correct. Both the R/3 system administrator and the user are authorized to maintain R/3 user id parameters, but there may be other users who are also authorized to do so.

Option C: Only the user himself - This option is incorrect. While users can maintain some of their own user id parameters, there are certain parameters that only the system administrator can change.

Option D: Only user SAP* - This option is incorrect. User SAP* is a default user id in SAP R/3 that is used for emergency access and is not authorized to maintain user id parameters.

Therefore, the correct answer is option B: Only the R/3 system administrator and the user.