A company wants to make sure that only one user from its Admin group has...

An Inline Policy is a policy that is embedded directly into an IAM user, group, or role. When you use an inline policy, you maintain a strict one-to-one relationship between the policy and the identity. Since the requirement is to grant a specific " permanent " right to only one specific user within a group without changing the shared group policy, an inline policy attached directly to that individual user is the correct approach.