Creating a custom CI class in the CMDB is a dictionary-level configuration activity and must be performed with the correct minimum privileges to ensure governance and upgrade safety in ServiceNow.

The sn_cmdb_admin role is required because it grants administrative access to CMDB structures, including CI class hierarchy management. This role ensures that changes align with CMDB governance controls and Data Foundations practices.

The personalize_dictionary role is also required because adding a new CI class involves creating or extending dictionary entries (tables, attributes, inheritance). Without dictionary-level access, a user cannot define new classes or attributes in the CMDB schema.

Option A is incorrect because sn_cmdb_admin alone is insufficient without dictionary privileges. Option B and D focus on form personalization, which affects UI layout only and does not allow creation of new CI classes. Additionally, itil_admin is not the correct role for schema-level CMDB changes.

Therefore, the minimal and correct role combination is sn_cmdb_admin and personalize_dictionary, making Option C the verified answer.